Optical architecture and channel plan employing multi-fiber configurations for data center network switching

ABSTRACT

Data center network architectures, systems, and methods that can reduce the cost and complexity of data center networks. Such data center network architectures, systems, and methods employ physical optical ring network and multi-dimensional network topologies and optical nodes to efficiently allocate bandwidth within the data center networks, while reducing the physical interconnectivity requirements of the data center networks. The respective optical nodes can be configured to provide various switching topologies, including, but not limited to, chordal ring switching topologies and multi-dimensional chordal ring switching topologies.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of the priority of U.S. ProvisionalPatent Application No. 61/498,931 filed Jun. 20, 2011 entitled DATACENTER NETWORK SWITCHING, and U.S. Provisional Patent Application No.61/554,107 filed Nov. 1, 2011 entitled DATA CENTER NETWORK SWITCHING.

FIELD OF THE INVENTION

The present application relates generally to data communicationssystems, and more specifically to optical data center networks,including the interconnection of data center servers, top-of-rackswitches, and aggregation switches using reduced cost coarse wavelengthdivision multiplexing (CWDM) transceivers, thereby enabling high switchinterconnectivity with easier fiber cabling.

BACKGROUND OF THE INVENTION

In recent years, university, government, business, and financial serviceentities, among others, have increasingly relied upon data centernetworks that incorporate racks of server computers (“servers”) toimplement application programs (“applications”) for supporting theirspecific operational requirements, including, but not limited to, database management applications, document and file sharing applications,searching applications, gaming applications, and financial tradingapplications. As such, data center networks are generally expanding interms of the number of servers incorporated therein, as well as thenetworking equipment needed to interconnect the servers foraccommodating the data transfer requirements of the applications thatthe servers are called upon to implement.

Conventional data center networks typically have hierarchicalarchitectures, in which each server co-located in a particular rack isconnected via one or more Ethernet connections to a top-of-rack Ethernetswitch (the “top-of-rack switch”). A plurality of such top-of-rackswitches form what is generally referred to as the “access layer”, whichis the lowest level of the hierarchical network architecture. The nexthigher level of the hierarchy is generally referred to as the“aggregation layer”, which can include a plurality of Ethernet switches(the “aggregation switch(es)”) and/or Internet protocol (IP) routers.Each top-of-rack switch in the access layer can be connected to one ormore aggregation switches and/or IP routers in the aggregation layer.The highest level of the hierarchy is generally referred to as the “corelayer”, which includes a plurality of IP routers (the “core switches”)that can be configured to provide ingress/egress points for the datacenter network. Each aggregation switch and/or IP router in theaggregation layer can be connected to one or more core switches in thecore layer, which, in turn, can be interconnected to one another. Insuch conventional data center networks, the interconnections between theracks of servers, the top-of-rack switches in the access layer, theaggregation switches/IP routers in the aggregation layer, and the coreswitches in the core layer, are typically implemented usingpoint-to-point Ethernet links.

Although the conventional data center networks described above have beenemployed to satisfy the operational requirements of many university,government, business, and financial service entities, such conventionaldata center networks have several drawbacks. For example, datacommunications between servers that are not co-located within the samerack may experience excessive delay (also referred to herein as“latency”) within the data center network, due in no small part to themultitude of switches and/or routers that the data may be required totraverse as it propagates up, down, and/or across the hierarchicalarchitecture of the network. Data communications between such serversmay also experience latency within the respective switches and/orrouters of the data center network due to excessive node and/or linkutilization. Further, because multiple paths may be employed to deliverbroadcast and/or multicast data to different destinations within thedata center network, such broadcast and/or multicast data may experienceexcessive latency skew. Such latency and/or latency skew may beexacerbated as the size of the data center network and/or its loadincreases. The hierarchical architecture of the data center network alsogenerally suffers from increasingly complex, but essentially fixed,fiber cabling requirements as the numbers of switches, routers, layers,and their interconnections are increased to handle the expansion of thedata center network.

It would therefore be desirable to have data center networkarchitectures, systems, and methods that avoid at least some of thedrawbacks of the conventional data center networks described above.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present application, data center networkarchitectures, systems, and methods are disclosed that can reduce thecost and complexity of data center networks. Such data center networkarchitectures, systems, and methods employ optical nodes utilizinghybrid spatial division multiplexing (SDM)/wavelength divisionmultiplexing (WDM) shifting channel plans on paired optical ports, whichcan be connected in a variety of physical cabled network topologies,including, but not limited to, physical rings and physical 2-dimensionaland higher dimensional toruses. The combination of a selected physicaltopology and a selected hybrid SDM/WDM shifting channel plan produces aswitching topology with increased interconnection density and reduceddiameter and link utilization, resulting in reduced latency and latencyskew. The optical nodes can include multicast/broadcast capable circuitswitches, such as electrical cross-point or electrical cross-barswitches, to increase the functionality of the optical nodes and thenetwork in which the optical nodes are deployed, allowing capacity to beshifted and switch hop counts to be reduced based on network traffic,application requirements, and/or deployment requirements. The networkmay be employed as a replacement for a multitude of top-of-rack switchesin the access layer, thereby reducing the network requirements of theaggregation layer and the core layer. Alternatively, the network may beemployed as a replacement for a multitude of aggregation switches and/orcore switches, thereby reducing the network requirements on theaggregation layer, the core layer, and the access layer.

In one aspect, each optical node includes a packet switch, such as anEthernet switch or an IP router. The packet switch has a plurality ofdownlink ports and a plurality of uplink ports. The packet switch can becommunicably coupled, by one or more of the downlink ports, through auser connection port on the optical node, to one or more externallyconnected devices, such as servers, external switches, external routers,or any other suitable computing or computer related devices, through oneor more downlinks. Each optical node can include several types of userconnection ports supporting various speeds, protocols, and/or physicalformats, including, but not limited to, 10 Gb/s Ethernet ports and QSFPports supporting 40 Gb/s Ethernet. The packet switch of one such opticalnode can be communicably coupled, by one or more of the uplink ports, tothe packet switch of another such optical node through one or moreuplinks. The packet switches of the optical nodes and theirinterconnection through the uplinks form what is referred to herein as a“switching topology”. It is noted that in such a switching topology, thepacket switches can be interconnected by multiple uplinks.

In another aspect, each optical node further includes a plurality ofoptical transmitters and a plurality of optical receivers (collectively,the “transceivers”) connected to its uplink ports. Each optical node canalso include at least one circuit switch, such as a cross-point switch,a cross-bar switch, or a more functional switch having the ability toswitch time slots of the signals on its inputs to time slots of thesignals on its outputs. The transceivers are operative to provideelectrical signals to the circuit switch, which, in turn, is operativeto provide a multitude of connections to the packet switch, therebyallowing the switching topology to be reconfigured. In an exemplaryaspect, the circuit switch is operative to multicast and/or broadcast asignal from its input to one, some, or all of its outputs. It is notedthat the switching topology that results when (1) there is no circuitswitch, or (2) the circuit switch is set to connect each of the opticalnode's transceivers to the optical node's packet switch uplink ports, isreferred to herein as the “base switching topology”. The base switchingtopology can be distinguished from the resultant switching topology,which results from reconfiguring the circuit switch.

In a further aspect, some or all of the user connection ports of eachoptical node are connected to the optical node's circuit switch, and theformat of uplink transmission is selected to match the format ofdownlink transmission, thereby enabling the reconfiguration of a userconnection port from one that internally connects to the optical node'spacket switch to one that internally connects to one of the opticalnode's transceivers (referred to herein as “direct attach”). A directattach is used to provide a direct attach link between two externallyconnected devices on different optical nodes, or between one externallyconnected device of an optical node and the packet switch of anotheroptical node. For example, a QSFP user connection port may provide asignal that is be converted into four (4) 10 GbE connections to one (1)to four (4) packet switches of other optical nodes, by separating outits four (4) 10 GbE component signals, and individually connecting thesignals by the circuit switch to four (4) transceivers, which canestablish connections to four (4) other transceivers at up to four (4)other optical nodes whose signals are connected, possibly through theircircuit switches, to one or more other internal packet switches orexternal devices using such direct attach.

Further, a subset of the four (4) 10 GbE component signals may beprovided for direct attach links, and the remainder of the 10 GbEcomponent signals may be provided for downlink transmission, by suitablyconnecting the 10 GbE component signals to the transceivers or thepacket switch, respectively. It is noted that, at any given opticalnode, there may be more transceivers than uplink ports, depending uponthe hardware configuration of the optical node, and whether or not anyuser connection ports are configured to be direct attach, therebyenabling terminated optical signals to be connected by the circuitswitch without disrupting any of the optical node's uplinks.

In still another aspect, each optical node further includes a pluralityof multi-fiber interfaces referred to herein as “optical ports”. Thenumber of optical ports in an optical node is indicative of the degreeof that optical node. For example, an optical node of degree-2 includestwo paired optical ports referred to herein as the “East” port and the“West” port. Further, an optical node of degree-4 includes two pairedoptical ports referred to herein as the East port and the West port, andtwo additional paired optical ports referred to herein as the “North”port and the “South” port. Such optical nodes can be physicallyinterconnected through their optical ports by a multitude of opticalfibers, which may be implemented using individual fiber cables or aplurality of multi-fiber cables, each with two or more fibers. In anexemplary aspect, the fibers interconnecting two optical nodes can becontained within a single multi-fiber cable with single multi-fiberconnectors connecting to the optical ports of the respective opticalnodes. The physical topology can be represented by a graph of nodes, inwhich the nodes of the graph correspond to the optical nodes, and edgesbetween the nodes of the graph indicate the optical node connections onone or more optical fibers. It is noted that the optical ports may bedistinct, or physically identical and assigned a name during or afterinstallation. For example, when the ports are physically identical,optical nodes of degree-2 on an optical ring network may be operative todiscover their neighboring optical nodes on the network, and to globallydecide which of their optical ports are to be designated as the Eastports and the West ports.

It is further noted that the switching topology may be different fromthe physical topology because some or all of the optical nodes mayutilize optical bypass, or may switch wavelengths through one or morecircuit switches after optical-to-electrical conversion, followed byelectrical-to-optical conversion on the same or different wavelength.For example, the physical topology may be an optical multi-fiber ringand the switching topology may be a chordal ring, or the physicaltopology may be a 2-dimensional torus and the switching topology may a2-dimensional chordal ring.

In yet another aspect, an optical node can have pairs of optical portsthat have internal optical paths, enabling all-optical bypass on amultitude of wavelengths between paired optical ports. The SDM/WDMoptical routing between the paired optical ports is referred to hereinas a “channel plan”, which specifies which wavelengths are to beterminated (e.g., dropped to an optical receiver, or added from anoptical transmitter) on which fibers, and which wavelengths are to beoptically routed from which input fiber to which output fiber throughthe optical node. For an optical node of degree-2, the East port and theWest port are paired optical ports. For an optical node of degree-4, theEast port and the West port are paired optical ports, and the North portand the South port are paired optical ports. In general, for an opticalnode with ports P1, P2, P3, . . . , ports P1 and P2 are paired opticalports, ports P3 and P4 are paired optical ports, etc. For purposes ofdiscussion, if two optical ports P1 and P2 are paired optical ports,then it is assumed that the channel plan in the direction from opticalport P1 to optical port P2 is the same as the channel plan in thedirection from optical port P2 to optical port P1. It is noted thatpaired optical ports implementing the same channel plan in eachdirection may or may not be physically identical, depending on how thefibers are to be connected, as well as the positions of the outbound andinbound fibers. It is further noted that different paired optical portscan support different channel plans. In addition, one of the wavelengthsin the SDM/WDM channel plan may be allocated to optical supervisorycontrol (OSC), or the OSC may be handled in a separate manner.

In a further aspect, at least two paired optical ports P1 and P2 of anoptical node can employ what is referred to herein as a singlewavelength “SDM shifting channel plan” in each direction. In thedirection from optical port P1 to optical port P2, an exemplary SDMshifting channel plan can be specified as follows. The inbound fibers ofoptical port P1 are divided into a plurality of inbound chordal groups,and the outbound fibers of optical port P2 are divided into an identicalset of outbound chordal groups, in which each inbound chordal group G ismatched to an outbound chordal group G′. For each inbound chordal groupG of optical port P1, the fibers 1, 2, 3, . . . r_(G) are numbered, inwhich “r_(G)” corresponds to the number of fibers in the inbound chordalgroup G. For each outbound chordal group G′ of optical port P2, thefibers 1, 2, 3, . . . r_(G′) are numbered, in which “r_(G′)” correspondsto the number of fibers in the outbound chordal group G′. Because theinbound chordal group G is matched to the outbound chordal group G′,r_(G′) is equal to r_(G). Fiber “f” of the inbound chordal group G isinternally routed to fiber “f-1” of the outbound chordal group G′ for fequal to 2, 3, . . . r_(G). The wavelength on fiber “1” of the inboundchordal group G is dropped by connecting it to one of the optical node'sreceivers. Further, the wavelength on fiber “r_(G′)” of the outboundchordal group G′ is added by connecting it to one of the optical node'stransmitters. The exemplary SDM shifting channel plan in the directionfrom optical port P2 to optical port P1 can be specified in a similarfashion. In an exemplary aspect, an optical node of degree-2 can includetwo paired optical ports, in which each optical port includes a singleconnectorized twelve (12) fiber cable divided into four (4) chordalgroups, namely, a first input chordal group of one (1) fiber, a firstoutput chordal group of one (1) fiber, a second input chordal group offive (5) fibers, and a second output chordal group of five (5) fibers.

In another aspect, at least two paired optical ports P1 and P2 of anoptical node can employ what is referred to herein as a hybrid “SDM/WDMshifting channel plan” in each direction. In the direction from opticalport P1 to optical port P2, an exemplary SDM/WDM shifting channel plancan be specified as follows. The inbound fibers of the optical port P1are divided into a plurality of inbound chordal groups, and the outboundfibers of the optical port P2 are divided into a set of identicaloutbound chordal groups. Each inbound chordal group G of the opticalport P1 is matched to an outbound chordal group G′ of the optical portP2, with the same number of fibers in each chordal group. For eachinbound chordal group G and its matching outbound chordal group G′, thefollowing steps are performed:

-   -   (1) the inbound fibers 1, 2, 3, . . . r are numbered, in which        “r” is the number of fibers of the inbound chordal group G;

(2) the outbound fibers 1, 2, 3, . . . r are numbered, in which “r” isthe number of fibers of the outbound chordal group G′, such that whenthe optical port P1 is connected to the optical port P2 of anotheroptical node, the first output fiber of the outbound chordal group G′ isconnected to the first input fiber of the inbound chordal group G, thesecond output fiber of the outbound chordal group G′ is connected to thesecond input fiber of the inbound chordal group G, etc.;

(3) a possibly empty set of wavelengths w_(f) is dropped from inputfiber f of the inbound chordal group G for f=1, 2, . . . r;

(4) a possibly empty set of wavelengths w′_(f′) is added to output fiberf′ of the outbound chordal group G′ for f′=1, 2, . . . r; and

(5) all wavelengths not in w_(f) or w′_(f-1) are routed from input fiberf of the inbound chordal group G to output fiber f′=f−1 of the outboundchordal group G′,

in which the number of times a wavelength w is added on an output fiberf′=1, . . . r of the outbound chordal group G′ equals the number oftimes that the same wavelength w is dropped on an input fiber f of theinbound chordal group G. The adding and dropping of wavelengths are donein sequence such that if the wavelength w is added at the output fiberf′, then it is dropped on the input fiber f≦f′before it can possibly beadded again to another output fiber f″<f′. The exemplary SDM/WDMshifting channel plan in the direction from optical port P2 to opticalport P1 can be specified in a similar fashion.

The SDM/WDM shifting channel plan allows the same wavelength w to bereused multiple times in a chordal group so long as each time after itis added onto an output fiber k of an output chordal group, thewavelength is extracted from the matching input chordal group on anequal or lower numbered input fiber j before being added again withinthe same output chordal group on an output fiber m<k. If a wavelength wis added on the output fiber k and next dropped on the input fiber j≦k,and if optical nodes implementing identical channel plans are cabled ina path or ring of sufficient length, then w will carry an opticalconnection that optically bypasses k−j optical nodes, producing a chordof length k−j+1. Adding and dropping wavelengths may be accomplishedwith the use of optical add/drop multiplexers, filters, or any othersuitable optical devices and/or techniques. Such devices can be placedin different positions within the optical node, or integrated in commonmodules in various ways, to accomplish the above-describedfunctionality.

With further regard to the SDM/WDM shifting channel plan, one or morechordal groups can employ the technique of injecting wavelengths only ontheir topmost outbound fiber, and dropping these wavelengths exactlyonce at one or more of the input fibers. One or more chordal groups canalso employ the technique of injecting wavelengths exactly once at oneor more of their output fibers, and dropping all wavelengths at theirbottommost fiber.

In addition, one or more chordal groups can employ the technique ofinjecting, on their topmost fiber, a wavelength from among the pluralityof all of the wavelengths in the channel plan, dropping that wavelengthon one of their input fibers k, adding that same wavelength back ontheir output fiber k−1, and extracting the same wavelength on theirbottommost fiber.

In still another aspect, inbound and outbound chordal groups that carrythe input and output portions of a duplex communication link of atransceiver can be contained within the same cable, which isadvantageous for cable wiring and fault tolerance. The positions of theinbound fibers in one optical port correspond to the positions of theoutbound fibers in the paired optical port, allowing the paired opticalports to be interconnected with a multi-fiber cable. For example, eachoptical port can connect to a single multi-fiber cable using a singlemulti-fiber connector. Further, the paired optical ports can implement acommon channel plan. The inbound and output fibers can also be containedin separate fiber cables, each possibly contained in multi-fiber bundlesand connectorized with multi-fiber connectors, with paired optical portsbeing physically identical, allowing the optical ports to beinterconnected by connecting outbound cables to inbound cables of apaired optical port.

In a further aspect, an optical node can include optical ports that donot have a corresponding optical port pair. For example, an optical nodecan have a West port, but no East port. In this case, the West port ofsuch an optical node functions as a terminal port. All wavelengths onall input fibers of that terminal port are terminated by transceiversthrough the use of optical multiplexers, optical de-multiplexers, or anyother suitable optical devices and/or techniques. For example, anoptical node of degree-1 can terminate each optical fiber on its soleoptical port. Further, an optical node of degree-3 can have a West portand an East port that are paired optical ports, and a South port that isa terminal port for terminating all of the wavelengths on all of thefibers of a South port/North port channel plan.

A plurality of optical nodes implementing various channel plans can beconnected in an optical network such that optical ports are connectedthrough a paired optical port to other optical ports that share the samechannel plan. For example, optical nodes, all of degree-2, can belogically laid out in a ring, and each optical node can be connected toits two neighboring optical nodes by a plurality of fibers, connectingthe East port of the optical node to the West port of one of itsneighboring optical nodes, and connecting the West port of the opticalnode to the East port of its other neighboring optical node. In anexemplary aspect, each type of optical port, e.g., the West port or theEast port, is keyed to allow physical connection to its East or Westport pair on another optical node. In another exemplary aspect, there isno physical distinction between the East and West ports. In a furtherexemplary aspect, each optical node is configured to implement a commonEast/West SDM/WDM shifting channel plan and an identical West/EastSDM/WDM shifting channel plan, and the switching topology is a chordalring network having a reduced fiber and/or wavelength count, allowingthe use of less costly optical transceivers and add/drop multiplexers.

For optical nodes that include a circuit switch, the chords of thechordal ring network can be reconfigured by effectively attaching two ormore chords to produce a chord of increased length.

In one aspect, a chordal ring network with N optical nodes, numberedn=0, 1, 2, . . . N−1, has chords of lengths r₁, r₂, . . . r_(C), suchthat the switch in optical node n is connected to the switch in itsneighboring optical nodes n+r_(c)(mod N) and n−r_(c) (mod N) with amultiplicity of s_(c)≧1 chords (c=1 . . . C), each chord representing anuplink.

The switching topology for such a chordal ring network can be denoted asR_(N)(r₁ ^(s) ¹ ; r₂ ^(s) ² ; r₃ ^(s) ³ ; . . . ; r_(C) ^(s) ^(C) ). Forexample, “R_(N)(1^(s) ¹ )” represents the switching topology of achordal ring network with N optical nodes, each optical node beingconnected to its two neighboring optical nodes by s₁ chords. Further,“R_(N)(1²;3)” represents the switching topology of a chordal ringnetwork, in which neighboring optical nodes are connected by two (2)chords, and optical nodes with two (2) intermediate optical nodesbetween them are connected by one (1) chord. Moreover, “R_(N) (1⁴; 2²;3²; 4²; 5²)” represents the switching topology of a chordal ring networkwith four (4) chords between neighboring optical nodes, two (2) chordsbetween optical nodes separated by one (1) other optical node, two (2)chords between optical nodes separated by two (2) other optical nodes,two (2) chords between optical nodes separated by three (3) otheroptical nodes, and two (2) chords between optical nodes separated byfour (4) other optical nodes.

In another aspect, a plurality of optical nodes of degree-2 arephysically connected in a ring, and the channel plan is selected suchthat the switching topology is denoted as R_(N)(1^(s) ¹ ; 2^(s) ² ;3^(s) ³ ; . . . ; (N/2)^(s) ^(c) ) for N even, and R_(N)(1^(s) ¹ ; 2^(s)² ; 3^(s) ³ ; . . . ; ((N−1)/2)^(s) ^(c) ) for N odd, providing a fullmesh with at least one chord (uplink) between each pair of opticalnodes. For example, “R₁₁(1⁴; 2²; 3²; 4²; 5²;)” represents a full meshswitching topology for eleven (11) optical nodes, in which neighboringoptical nodes are connected by four (4) chords, and non-neighboringoptical nodes are connected by two (2) chords. Further, “R₁₂(1⁴; 2²; 3²;4²; 5²; 6²)”) represents a full mesh switching topology for twelve (12)optical nodes, in which neighboring optical nodes, and optical nodeshalfway around the ring separated by five (5) optical nodes betweenthem, are connected by four (4) chords, and all other pairs of opticalnodes are connected by two (2) chords.

The SDM shifting channel plan requires F=2Σ_(c=1) ^(C) s_(c)*r_(c)fibers between physically adjacent optical nodes to create a full meshswitching topology. For example, the switching topology denoted asR₁₁(1⁴; 2²; 3²; 4²; 5²) provides a full mesh on eleven (11) opticalnodes, and requires a total of sixty-four (64) fibers between everyoptical node in the physical ring. Using the SDM/WDM shifting channelplan, the switching topology R₁₁(1⁴; 2²; 3²; 4²; 5²) can be implementedusing twelve (12) fibers between optical nodes, using six (6) distinctwavelengths, by forming two (2) chordal groups per direction, in whichthe first chordal group in each direction includes a single fibercarrying the four (4) chords on wavelengths w1, w2, w3, and w4, and thesecond chordal group in each direction includes five (5) fibers carryingthe remaining chords. Wavelengths w1, w2, w3, and w4 are added to outputfiber “5” of the chordal group, wavelengths w5 and w6 are added tooutput fiber “4” of the chordal group, wavelengths w1 and w2 are droppedon input fiber “4” and added on output fiber “3”, wavelengths w1, w2,w3, w4, w5, and w6 are dropped on input fiber “1” so that wavelengths w1and w2 implement two (2) chords of length 2 and 3, wavelengths 3 and 4implement chords of length 5, and wavelengths w5 and w6 implement two(2) chords of length 4. Alternatively, the switching topology R₁₁(1⁴;2²; 3²; 4²; 5²) can be implemented using twelve (12) fibers betweenoptical nodes, using eight (8) distinct wavelengths, by forming two (2)chordal groups per direction, in which the first chordal group in eachdirection includes a single fiber carrying the four (4) ring chords onwavelengths w1, w2, w3, and w4, and the second chordal group in eachdirection includes five (5) fibers carrying the remaining chords.Wavelengths w1, w2, w3, w4, w5, w6, w7, and w8 are added to output fiber“5” of the chordal group in each direction, wavelengths w1 and w2 aredropped on input fiber “4”, w3 and w4 are dropped on input fiber “3”, w5and w6 are dropped on input fiber “2”, and w7 and w8 are dropped oninput fiber “1”.

Accordingly, there are a multitude of possible SDM/WDM shifting channelplans for the same chordal ring topology, some of which may provideadvantages in terms of optical loss, the availability of opticalcomponents, etc., whereas the SDM shifting channel plan is uniquelydetermined by the selected chordal ring topology. For example, theswitching topology denoted as R₁₁(1; 2; 3; 4; 5) requires thirty (30)fibers using the SDM shifting channel plan. Further, the switchingtopology R₁₁(1; 2; 3; 4; 5) requires ten (10) fibers between neighboringoptical nodes and three (3) distinct wavelengths using the SDM/WDMshifting channel plan, by forming chordal groups of size five (5) ineach direction, adding the 1^(st), 2^(nd), and 3^(rd) wavelengths onoutput fiber “5” in each direction, dropping the 2^(nd) wavelength atoutput fiber “4”, adding the 2^(nd) wavelength at output fiber “3”,dropping the 3^(rd) wavelength at output fiber “2”, adding the 3^(rd)wavelength at output fiber “2”, and dropping the 1^(st), 2^(nd), and3^(rd) wavelengths at input fiber “1”. It is noted that, if the fullmesh were implemented directly with a pair of fibers between each pairof optical nodes, instead of being implemented in a physical ring usingmulti-fiber cables, then a full mesh for eleven (11) optical nodes wouldrequire a total of 11*10=110 fibers, which is the same number of fibersthat would be required using the SDM/WDM shifting channel plan, whereasusing the SDM shifting channel plan would require a total of 330 fibers.

In a further aspect, the channel plan can be selected such that everyoptical node in the ring is connected by at least one chord to everyother optical node in the ring, thereby producing a full mesh switchingtopology. It is noted that the circuit switches included in the opticalnodes may be employed to connect a multitude of chords for producing thefull mesh switching topology. For example, a full mesh can be achievedwith twelve (12) optical nodes by using a SDM/WDM shifting channel planwith six (6) wavelengths and twelve (12) fibers between neighboringoptical nodes to implement the switching topology R₁₂(1⁴; 2²; 3²; 4²;5²) (which is not a full mesh), and using the circuit switches to joinsome chords of length 1 and 5 to implement the full mesh switchingtopology R₁₂(1³; 2²; 3²; 4²; 5¹; 6¹).

In other aspects, optical nodes of degree-2 and optical nodes ofdegree-1 can be connected to form a physical path topology, in which theoptical nodes of degree-1 are the endpoints of the physical pathtopology, and the switching topology is a chordal path topology.Further, a q-dimensional torus physical topology can be formed usingoptical nodes of degree-2q, in which the optical nodes in each dimensionare connected in a physical ring, thereby forming multi-dimensionalchordal ring switching topologies. Data communications between opticalnodes that are not within the same dimension can be routed through oneor more packet switches and/or one or more circuit switches to createone or more inter-dimensional uplinks. For example, a 2-dimensionaltorus physical topology can be formed using optical nodes of degree-4logically laid out in a grid with each optical node connected to itsfour (4) neighboring optical nodes through its East, West, North, andSouth ports with a multitude of fibers. In such a grid, the first andlast optical nodes in a row are regarded as being neighboring opticalnodes, and the first and last optical nodes in a column are likewiseregarded as being neighboring optical nodes. For example, the columns ofthe grid can represent neighboring racks in a data center network. Therows of the grid support the East/West channel plan, and the columns ofthe grid support the North/South channel plan. Data communicationsbetween optical nodes that are not within the same row or column can beelectrically routed through one or more packet switches and/or one ormore circuit switches to create one or more uplinks between the opticalnodes. It is noted that the channel plans can be selected to form a fullmesh in each row and column of the grid used to form the torus network.

It is further noted that optical ports that are not paired may implementdifferent channel plans, and therefore may or may not be able to connectto one another, depending on the specifics of the selected channelplans. In such a case, for example, the East/West ports of an opticalnode of degree-4 can form a ring using a first subset of optical nodesof degree-2 having a common East/West channel plan, and the North/Southports of the optical node of degree-4 can form a ring using a secondsubset of optical nodes of degree-2 having the same or differentEast/West channel plan, in which the North/South channel plan of theoptical node of degree-4 matches the East/West channel plan of thesecond subset of optical nodes of degree-2.

In another aspect, optical nodes of degree-4, or optical nodes of anyother suitable degree, can be connected to one another to implementother switching topologies. For example, the optical ports of suchoptical nodes can be connected to paired optical ports of other suchoptical nodes, creating switching topologies that can includeoverlapping chordal rings and/or paths, in which one or more of theoptical nodes can exist in more than one chordal ring and/or path.

In still another aspect, low latency and low latency skew multicastingand broadcasting can be achieved by configuring the circuit switches ofa plurality of optical nodes to establish duplex uplinks from a sourceor origin packet switch to a set of primary destination packet switches,using a plurality of the source packet switch's uplink ports and simplexconnections from the same source packet switch and uplink ports to aplurality of secondary packet switches, with one or more circuitswitches establishing a simplex multicast or broadcast connection fromone of its input ports to a plurality of its output ports, therebyenabling data multicasting and broadcasting from a server connected tothe source packet switch to a plurality of servers connected to the samepacket switch and/or different packet switches. In an exemplary aspect,the transmitting uplink ports on the secondary set of destination packetswitches are muted. In another exemplary aspect, the transmitting uplinkports on the secondary set of destination packet switches are not muted,but data transmission is disabled by the circuit switches connected tothe secondary transmitting uplink ports. In still another exemplaryaspect, the transmitting uplink ports on one or more of the secondarypacket switches are enabled and employed in separate multicast orbroadcast communications. In a further aspect, the plurality of opticalnodes are on an optical ring network, one of the destination packetswitches is the source packet switch, and an outbound signal from anuplink of the source packet switch is either looped back at thatswitch's circuit switch onto its receiver uplink port, or routed throughthe network, for example, by routing the outbound signal around the ringso that it connects back on the source packet switch uplink port,thereby establishing the duplex connection. For example, in a physicalring network, a duplex connection can be established from the sourcepacket switch to itself (using two uplink ports connected through thenetwork), and the outbound signal can be dropped at a plurality ofintermediate packet switches to establish multicast or broadcast simplexcommunications from the source packet switch to the destination packetswitches.

By employing a passive shift strategy for the fibers at each opticalnode, combined with a fixed and passive wavelength add/drop scheme,2-dimensional as well as higher dimensional chordal ring networks can beconstructed using a reduced number of communications channels (e.g.,fibers, wavelengths, time slots). The optical nodes can be configured tobe substantially identical to one another. Further, each optical nodecan be configured to include a circuit switch to enable dynamicconfiguration of network chords for tailoring the network topology tothe network traffic, reducing the network diameter, and/or increasingthe density of the network topology. Each optical node can also includean electrical Ethernet packet switch to enable a fully integrated, layer0/1/2/3 configurable, switching network with reduced fiberinterconnection complexity, WDM hardware requirements, circuit switchsize, packet switch size, and processing requirements. Higher degreephysical topologies as well as alternate topologies can also beemployed. In addition, the multi-fiber bundles can be keyed to reducefiber cabling errors.

Other features, functions, and aspects of the invention will be evidentfrom the Drawings and/or the Detailed Description of the Invention thatfollow.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention will be more fully understood with reference to thefollowing Detailed Description of the Invention in conjunction with thedrawings of which:

FIG. 1 is a block diagram of an exemplary optical ring network thatincludes a plurality of optical nodes of degree-2, configured inaccordance with the present application;

FIG. 2 is a block diagram of an exemplary optical node of degree-2included in the optical ring network of FIG. 1;

FIG. 3 a is a schematic diagram of an exemplary switch module, and anexemplary optical MUX/DMUX module, included in the optical node of FIG.2;

FIGS. 3 b-3 c are schematic diagrams of the optical MUX/DMUX moduleimplemented on the optical node of FIG. 3 a;

FIG. 4 is a block diagram of the optical ring network of FIG. 1,illustrating the mesh connectivity that can be achieved when therespective optical nodes are configured in accordance with the opticalnode of FIG. 2;

FIG. 5 is a block diagram of an exemplary optical chordal ring networkthat includes a plurality of optical nodes configured in accordance withthe optical node of FIG. 2;

FIG. 6 is a schematic diagram of an exemplary switch module that can beimplemented on the optical node of FIG. 3 a;

FIG. 7 a is a block diagram of an exemplary optical ring network,including a plurality of optical nodes configured to support a lowlatency multicast data channel on the optical ring network;

FIG. 7 b is a block diagram of the optical ring network of FIG. 7 a, inwhich the plurality of optical nodes are configured to support a lowlatency broadcast data channel on the optical ring network;

FIG. 7 c is a block diagram of the optical ring network of FIG. 7 a, inwhich the plurality of optical nodes are configured to support a flywaychannel on the optical ring network;

FIG. 8 is a flow diagram of an exemplary method of operating the opticalnode of FIG. 2 for achieving low signal transport latency within theoptical node;

FIG. 9 a is a block diagram of an exemplary optical torus network thatincludes a plurality of optical nodes of degree-4, configured inaccordance with the optical node of FIG. 2;

FIG. 9 b is a block diagram of an exemplary optical node of degree-4included in the optical torus network of FIG. 9 a;

FIG. 9 c is a block diagram of an exemplary chordal path network thatincludes a plurality of optical nodes of degree-2, and a plurality ofoptical nodes of degree-1;

FIG. 9 d is a block diagram of an exemplary Manhattan Street physicaltopology that includes a plurality of optical nodes of degree-2, aplurality of optical nodes of degree-3, and a plurality of optical nodesof degree-4;

FIGS. 10 a-10 b are schematic diagrams of an exemplary alternativeembodiment of the optical MUX/DMUX module of FIGS. 3 b-3 c;

FIG. 11 is a schematic diagram of a further exemplary alternativeembodiment of the optical MUX/DMUX module of FIG. 3 b;

FIGS. 12 a-12 b are schematic diagrams of another exemplary alternativeembodiment of the optical MUX/DMUX module of FIGS. 3 b-3 c;

FIG. 13 a is a diagram of an exemplary multi-core optical fiber that maybe employed in conjunction with the optical MUX/DMUX module of FIGS. 3b-3 c;

FIG. 13 b is a schematic diagram of the optical MUX/DMUX module of FIG.3 b implemented in conjunction with the multi-core optical fiber of FIG.13 a;

FIG. 14 a is a block diagram of an exemplary cross-point switch andpacket switch that can be included in the switch module implemented onthe optical node of FIG. 3 a;

FIG. 14 b is a block diagram of an exemplary alternative embodiment ofthe cross-point switch and packet switch of FIG. 14 a;

FIG. 14 c is a block diagram of a further exemplary alternativeembodiment of the cross-point switch and packet switch of FIG. 14 a; and

FIG. 15 is a schematic diagram of alternative embodiments of theexemplary switch module, and the exemplary optical MUX/DMUX module, ofFIG. 3 a.

DETAILED DESCRIPTION OF THE INVENTION

The disclosures of U.S. Provisional Patent Application No. 61/498,931filed Jun. 20, 2011 entitled DATA CENTER NETWORK SWITCHING, U.S.Provisional Patent Application No. 61/554,107 filed Nov. 1, 2011entitled DATA CENTER NETWORK SWITCHING, and U.S. patent application Ser.No. 13/528,211 filed Jun. 20, 2012 entitled OPTICAL JUNCTION NODES FORUSE IN DATA CENTER NETWORKS, are incorporated herein by reference intheir entirety.

Data center network architectures, systems, and methods are disclosedthat can reduce the cost and complexity of data center networks. Suchdata center network architectures, systems, and methods employ physicaloptical ring network topologies and optical nodes utilizing hybridspatial division multiplexing (SDM)/wavelength division multiplexing(WDM) shifting channel plans on paired optical ports, which can beconnected in a variety of physical cabled network topologies, including,but not limited to, physical rings and physical 2-dimensional and higherdimensional toruses to efficiently allocate bandwidth within data centernetworks, while reducing the physical interconnectivity requirements ofthe data center networks.

FIG. 1 depicts an illustrative embodiment of an exemplary optical ringnetwork 100 that includes a plurality of optical nodes 1 through 11, inaccordance with the present application. It is noted that the opticalring network 100 depicted in FIG. 1 includes eleven (11) optical nodes1-11 for purposes of illustration, and that any other suitable number ofoptical nodes may be included in the optical ring network 100. Asemployed herein, the term “optical node” refers to a primary networknode providing packet communication services to its externally connecteddevices. Each of the plurality of optical nodes 1-11 can be communicablycoupled, through one or more of the user connection ports, to one ormore external computerized devices, such as one or more server computers(“servers”; see, e.g., server(s) 203 of FIG. 2) for running one or moreapplication programs (“applications”), for storing data, etc. Suchservers can operate either alone or in association with one or moreother servers, which can be communicably coupled to the same opticalnode, or separate optical node(s), through one or more of the uplinkports. For example, the packet switches within the plurality of opticalnodes 1-11 and the respective server(s) coupled thereto can communicatethrough the various uplink/downlink ports using a 10 Gb Ethernetprotocol, or any other suitable protocol. Each of optical nodes 1-11 canemploy optical wavelength division multiplexing (WDM), dense wavelengthdivision multiplexing (DWDM), or coarse wavelength division multiplexing(CWDM). Further, links interconnecting the respective optical nodes 1-11on the optical ring network 100 can be implemented using a singleoptical fiber pair configuration, or multi-fiber pair configurationsincluding, e.g., one or more multi-fiber ribbon cables (e.g., MTP®multi-fiber ribbon cables).

FIG. 2 depicts an exemplary configuration of optical node 1 on theoptical ring network 100 (see FIG. 1). It is noted that the otheroptical nodes 2-11 on the optical ring network 100 can have aconfiguration like that of optical node 1. As shown in FIG. 2, opticalnode 1 is an optical node of degree-2 that includes two paired opticalports 212, 214 referred to herein as the “East” port 212 and the “West”port 214. Optical node 1 also includes an optical MUX/DMUX module 202, aswitch module 209, and an optical backplane with a twenty-four (24)fiber connector 208, such as an HBMT™ connector or any other suitableconnector. Optical node 1 further includes a first bundle 206 of 12optical fibers connected between the optical MUX/DMUX module 202 and theconnector 208 in the East (“clockwise”) direction along the optical ringnetwork 100 (e.g., from optical node 1 toward optical node 2; see FIG.1), and a second bundle 204 of 12 optical fibers connected between theoptical MUX/DMUX module 202 and the connector 208 in the West (“counterclockwise”) direction along the optical ring network 100 (e.g., fromoptical node 1 toward optical node 11; see FIG. 1). It is noted thatsuch optical MUXs (multiplexers) can include, but are not limited to,thin film filters, arrayed waveguide routers, fused biconic tapers,waveguides, and optical multiplexers with multi-port add capability.Further, such optical DMUXs (de-multiplexers) can include, but are notlimited to, thin film filters, arrayed waveguide routers, fused biconictapers, waveguides, and optical de-multiplexers with multi-port dropcapability.

Using the optical MUX/DMUX module 202 included in optical node 1 (seeFIG. 2), a plurality of wavelength channel numbers can be mapped intoactual physical wavelength numbers based on a predetermined channelplan, such as an ITU (International Telecommunications Union) opticalCWDM channel plan (see, e.g., Table I), or any other suitable channelplan. With reference to an exemplary ITU optical CWDM channel plan (seeTable I), a total of eight (8) wavelength channels 1 through 8 cansupport a single product code for the optical MUX/DMUX module 202. It isnoted that any other suitable number of wavelength channels can beemployed to support any other suitable product code(s) for the opticalMUX/DMUX module 202.

TABLE I Channel Plan Mapped into ITU CWDM Wavelength Channel # ITU CWDM(nm) 1 1271 2 1291 3 1311 4 1331 5 1351 6 1371 7 1391 8 1411

As further shown in FIG. 2, the switch module 209 included in opticalnode 1 is coupled between the optical MUX/DMUX module 202 and theserver(s) 203. Optical node 1 and the server(s) 203 can therefore becommunicably coupled to one another by one or more bidirectional links205, 207, each of which is operatively connected between the switchmodule 209 and the server(s) 203.

FIG. 3 a depicts a detailed view of optical node 1, including theoptical MUX/DMUX module 202 and the switch module 209. As shown in FIG.3 a, the optical MUX/DMUX module 202 includes a pair of optical filterconfigurations 301, 303 that can be used to implement a predeterminedchannel plan, such as the exemplary ITU optical CWDM channel plan ofTable I, or any other suitable channel plan. As described herein, theoptical filter configurations 301, 303 are configured to implement whatis referred to herein as a hybrid SDM/WDM shifting channel plan. It isnoted that the other optical nodes 2-11 on the optical ring network 100(see FIG. 1) can include optical filter configurations like those ofoptical node 1. The optical filter configuration 301 includes aplurality of inputs (generally indicated by reference numeral 380)operatively connected to optical fibers #1 through #6 in the West(counter clockwise) direction along the optical ring network 100, and aplurality of outputs (generally indicated by reference numeral 382)operatively connected to optical fibers #1 through #6 in the East(clockwise) direction along the optical ring network 100. Likewise, theoptical filter configuration 303 includes a plurality of inputs(generally indicated by reference numeral 384) operatively connected tooptical fibers #7 through #12 in the East (clockwise) direction alongthe optical ring network 100, and a plurality of outputs (generallyindicated by reference numeral 386) operatively connected to opticalfibers #7 through #12 in the West (counter clockwise) direction alongthe optical ring network 100. The plurality of inputs 384 and theplurality of outputs 382 are included in the East port 212 (see FIG. 2)of optical node 1, and the plurality of inputs 380 and the plurality ofoutputs 386 are included in the West port 214 (see FIG. 2) of opticalnode 1. For example, optical fibers #1 through #12 can be implementedusing one or more multi-fiber ribbon cables. It is noted that suchmulti-fiber ribbon cables are described herein as including twelve (12)optical fibers for purposes of illustration, and that any other suitablenumber of optical fibers within such multi-fiber ribbon cables may beemployed.

With reference to optical node 1 (see FIG. 3 a), the plurality of inputs380 of the optical filter configuration 301 are operative to receiveoptical signals carried by the respective optical fibers #1-#6 fromoptical node 11 (see FIG. 1), and the plurality of outputs 382 of theoptical filter configuration 301 are operative to send optical signalson the respective optical fibers #1-#6 to optical node 2 (see FIG. 1).In the East (clockwise) direction along the optical ring network 100(see FIG. 1), optical node 1 is therefore communicably coupled tooptical node 11 by the plurality of inputs 380, which are in apredetermined sequence corresponding to the fibers #1 through #6.Further, optical node 1 is communicably coupled, in the East (clockwise)direction along the optical ring network 100, to optical node 2 by theplurality of outputs 382, which are also in the predetermined sequencecorresponding to the fibers #1 through #6. The optical filterconfiguration 301 further includes a plurality of optical connectionpaths disposed between the respective inputs and outputs 380, 382, suchas optical connection paths 388, 389, 390, 391, which are configured toimplement the predetermined SDM/WDM shifting channel plan.

For example, with reference to the optical filter configuration 301 (seeFIG. 3 a), each of the plurality of inputs 380, as well as each of theplurality of outputs 382, have specific positions in the predeterminedsequence corresponding to optical fibers #1 through #6. To implement thepredetermined SDM/WDM shifting channel plan, at least some of theplurality of optical connection paths are configured to communicablycouple a respective input with a respective output, such that thespecific positions of the respective input and the respective outputdiffer by at least one position in the predetermined sequence. Forexample, the optical connection path 388 is configured to communicablycouple the output that has a position in the predetermined sequencecorresponding to the fiber #5 (on the East side), with the input thathas a position in the predetermined sequence corresponding to the fiber#6 (on the West side). Further, the optical connection path 389 isconfigured to communicably couple the output that has a position in thepredetermined sequence corresponding to the fiber #4 (on the East side)with the input that has a position in the predetermined sequencecorresponding to the fiber #5 (on the West side). Moreover, the opticalconnection path 390 is configured to communicably couple the output thathas a position in the predetermined sequence corresponding to the fiber#3 (on the East side) with the input that has a position in thepredetermined sequence corresponding to the fiber #4 (on the West side).In addition, the optical connection path 391 is configured tocommunicably couple the output that has a position in the predeterminedsequence corresponding to the fiber #2 (on the East side) with the inputthat has a position in the predetermined sequence corresponding to thefiber #3 (on the West side).

The plurality of inputs 384 of the optical filter configuration 303 (seeFIG. 3 a) are operative to receive optical signals carried by therespective optical fibers #7 through #12 from optical node 2 (see FIG.1), and the plurality of outputs 386 of the optical filter configuration303 (see FIG. 3 a) are operative to send optical signals on therespective optical fibers #7 through #12 to optical node 11 (see FIG.1). In the West (counter clockwise) direction along the optical ringnetwork 100, optical node 1 is therefore communicably coupled to opticalnode 2 by the plurality of inputs 384, which are in a predeterminedsequence corresponding to the fibers #7 through #12. Further, opticalnode 1 is communicably coupled, in the West (counter clockwise)direction along the optical ring network 100, to optical node 11 by theplurality of outputs 386, which are also in the predetermined sequencecorresponding to the fibers #7 through #12. The optical filterconfiguration 303 further includes a plurality of optical connectionpaths disposed between the respective inputs 384 and the respectiveoutputs 386, including optical connection paths 392, 393, 394, 395,which are also configured to implement the predetermined SDM/WDMshifting channel plan.

With reference to the optical filter configuration 303 (see FIG. 3 a),each of the plurality of inputs 384, as well as each of the plurality ofoutputs 386, have specific positions in the predetermined sequencecorresponding to optical fibers #7 through #12. To further implement thepredetermined SDM/WDM shifting channel plan, at least some of theplurality of optical connection paths disposed between the respectiveinputs and outputs 384, 386 are configured to communicably couple arespective input with a respective output, such that the specificpositions of the respective input and the respective output differ by atleast one position in the predetermined sequence. For example, theoptical connection path 392 is configured to communicably couple theoutput that has a position in the predetermined sequence correspondingto the fiber #8 (on the West side) with the input that has a position inthe predetermined sequence corresponding to the fiber #9 (on the Eastside). Further, the optical connection path 393 is configured tocommunicably couple the output that has a position in the predeterminedsequence corresponding to the fiber #9 (on the West side) with the inputthat has a position in the predetermined sequence corresponding to thefiber #10 (on the East side). Moreover, the optical connection path 394is configured to communicably couple the output that has a position inthe predetermined sequence corresponding to the fiber #10 (on the Westside) with the input that has a position in the predetermined sequencecorresponding to the fiber #11 (on the East side). In addition, theoptical connection path 395 is configured to communicably couple theoutput that has a position in the predetermined sequence correspondingto the fiber #11 (on the West side) with the input that has a positionin the predetermined sequence corresponding to the fiber #12 (on theEast side).

As shown in FIG. 3 a, the switch module 209 includes a packet switch346, which can be implemented using electronic packet switch technology.For example, the packet switch 346 can be implemented as an Ethernetpacket switch, an Internet protocol (IP) packet router, or any othersuitable switch. The switch module 209 further includes a circuit switch348 disposed between the packet switch 346 and the plurality of opticalconnection paths of the respective optical filter configurations 301,303. For example, the circuit switch 348 can be implemented as across-bar switch, a cross-point switch, or any other suitable switch.The circuit switch 348 can receive, in electrical form, one or moresignals sourced from one or more of the inputs 380, 384, and can provideone or more of the signals for subsequent forwarding as optical signalsto one or more of the outputs 382, 386. Such optical signals can each beassociated with a layer-1 (L1) lightpath extending at least partiallythrough optical node 1. The switch module 209 further includes aprocessor 349 for local control and/or configuration of the packetswitch 346 and/or the circuit switch 348. For example, the processor 349can receive instructions for such control and/or configuration of thepacket switch 346 and/or the circuit switch 348 from an external centralprocessor over one or more optical supervisory control (OSC) channels(e.g., an OSC channel corresponding to an optical DMUX filter (“dropmodule”) 302 and an optical MUX filter (“add module”) 310, and/or an OSCchannel corresponding to a drop module 326 and an add module 320; seeFIG. 3 a), which are discussed further below. The processor 349 can alsobe configured to receive such instructions via a network managementport. The switch module 209 also includes a plurality of inputtransceivers 338.1-338.12 and a plurality of output transceivers340.1-340.12 disposed between the circuit switch 348 and the opticalfilter configuration 301, as well as a plurality of input transceivers344.1-344.12 and a plurality of output transceivers 342.1-342.12disposed between the circuit switch 348 and the optical filterconfiguration 303. It is noted that clock and data recovery (CDR) may beimplemented, as required and/or as desired, either as an integrated partof the circuit switch 348, or external to the circuit switch 348, suchas at locations corresponding to CDR circuits 396, 397, 398, 399 (seeFIG. 3 a). As further shown in FIG. 3 a, the optical filterconfiguration 301 includes a plurality of optical DMUX filters (“dropmodules”) 304, 306, and a plurality of optical MUX filters (“addmodules”) 308, 312, 314, 316, 318. The plurality of optical connectionpaths of the optical filter configuration 301, including the opticalconnection paths 388-391, can be configured to implement one or morewavelength channels, such as WDM wavelength channels. Moreover, each ofthe drop modules 304, 306 is operative to separate one or more opticalsignals, such as WDM wavelength channel signals allocated to one or morepredetermined WDM wavelength channels, from an optical signal carried bya respective optical connection path within the optical filterconfiguration 301. In addition, each of the add modules 308, 312, 314,316, 318 is operative to add one or more optical signals, such as WDMwavelength channel signals allocated to one or more predetermined WDMwavelength channels, to a respective optical connection path within theoptical filter configuration 301.

Like the optical filter configuration 301, the optical filterconfiguration 303 includes a plurality of optical DMUX filters (“dropmodules”) 324, 328, and a plurality of optical MUX filters (“addmodules”) 320, 322, 330, 332, 334, 336. The plurality of opticalconnection paths of the optical filter configuration 303, including theoptical connection paths 392-395, can be configured to implement one ormore wavelength channels, such as WDM wavelength channels. Moreover,each of the drop modules 324, 328 is operative to separate one or moreoptical signals, such as WDM wavelength channel signals allocated to oneor more predetermined WDM wavelength channels, from an optical signalcarried by a respective optical connection path within the opticalfilter configuration 303. In addition, each of the add modules 320, 322,330, 332, 334, 336 is operative to add one or more optical signals, suchas WDM wavelength channel signals allocated to one or more predeterminedWDM wavelength channels, to a respective optical connection path withinthe optical filter configuration 303.

The plurality of input transceivers 338.1-338.12 are operative toperform optical-to-electrical (O-E) conversion of the wavelength channelsignals separated from the respective optical connection paths of theoptical filter configuration 301, and the plurality of outputtransceivers 340.1-340.12 are operative to perform electrical-to-optical(E-O) conversion of the wavelength channel signals to be added to theoptical connection paths of the optical filter configuration 301.Likewise, the plurality of input transceivers 344.1-344.12 are operativeto perform optical-to-electrical (O-E) conversion of the wavelengthchannel signals separated from the respective optical connection pathsof the optical filter configuration 303, and the plurality of outputtransceivers 342.1-342.12 are operative to perform electrical-to-optical(E-O) conversion of the wavelength channel signals to be added to theoptical connection paths of the optical filter configuration 303. Thecircuit switch 348 is operative to receive, in electrical form from oneor more of the input transceivers 338.1-338.12, 344.1-344.12 overconnection paths 370 and/or connection paths 372, one or more wavelengthchannel signals separated from one or more of the optical connectionpaths within the optical filter configuration 301 and/or the opticalfilter configuration 303. The circuit switch 348 is further operative toselectively provide one or more of the wavelength channel signals to thepacket switch 346 over connection paths 374, and/or to selectivelyprovide, over connection paths 376 and/or connection paths 378, one ormore of the wavelength channel signals to one or more of the outputtransceivers 340.1-340.12, 342.1-342.12. Such wavelength channel signalsare, in turn, provided by the output transceivers 340.1-340.12,342.1-342.12 in optical form to one or more of the add modules 308, 312,314, 316, 318, 320, 322, 330, 332, 334, 336, for subsequent addition toone or more of the optical connection paths within the optical filterconfiguration 301 and/or the optical filter configuration 303. It isunderstood that the input transceivers, e.g., the input transceivers338.1-338.12, 344.1-344.12, may be integrated into a single device.Likewise, the output transceivers, e.g., the output transceivers340.1-340.12, 342.1-342.12, may be integrated into a single device.

FIGS. 3 b and 3 c depict detailed views of the optical filterconfigurations 301, 303, respectively, included in the optical MUX/DMUXmodule 202 (see FIGS. 2, 3 a). FIGS. 3 b-3 c depict how the twenty-four(24) single or multi-mode fibers (e.g., “fiber #1 (in)” through “fiber#12 (in)”, and “fiber #1 (out)” through “fiber #12 (out)”; see FIGS. 3b, 3 c) from one or more multi-fiber ribbon cables can be routed withinthe respective optical filter configurations 301, 303 for connection tothe plurality of add modules 308, 312, 314, 316, 318, 320, 322, 330,332, 334, 336, and the plurality of drop modules 304, 306, 324, 328.FIG. 3 b depicts the optical filter configuration 301 for connectingoptical node 1 between optical node 11 and optical node 2 on the opticalring network 100 (see FIG. 1) to allow optical signal transmission inthe “West In”/“East Out” direction. FIG. 3 c depicts the optical filterconfiguration 303 for connecting optical node 1 between optical node 11and optical node 2 on the optical ring network 100 (see FIG. 1) to allowoptical signal transmission in the “East In”/“West Out” direction.

More specifically, FIGS. 3 b and 3 c depict an SDM/WDM shifting channelplan that employs twelve (12) fibers between optical nodes, using eight(8) distinct wavelengths indicated by reference numerals 1, 2, 3, 4, 5,6, 7, 8. Two chordal groups can be formed in the inbound direction onthe West port 214 (see also FIG. 2), and two chordal groups can beformed in the outbound direction on the East port 212 (see also FIG. 2).For example, a first chordal group in the inbound direction on the Westport 214 can include a single fiber, namely, fiber #1 (in) (see FIG. 3b), and a matching first chordal group in the outbound direction on theEast port 212 can likewise include a single fiber, namely, fiber #1(out) (see FIG. 3 b). Further, a second chordal group in the inbounddirection on the West port 214 can include five (5) fibers, namely,fiber #2 (in), fiber #3 (in), fiber #4 (in), fiber #5 (in), and fiber #6(in) (see FIG. 3 b), and a matching second chordal group in the outbounddirection on the East port 212 can likewise include five (5) fibers,namely, fiber #2 (out), fiber #3 (out), fiber #4 (out), fiber #5 (out),and fiber #6 (out) (see FIG. 3 b). Similarly, a first chordal group inthe inbound direction on the East port 212 can include a single fiber,namely, fiber #7 (in) (see FIG. 3 c), and a matching first chordal groupin the outbound direction on the West port 214 can likewise include asingle fiber, namely, fiber #7 (out) (see FIG. 3 c). Further, a secondchordal group in the inbound direction on the East port 212 can includefive (5) fibers, namely, fiber #8 (in), fiber #9 (in), fiber #10 (in),fiber #11 (in), and fiber #12 (in) (see FIG. 3 c), and a matching secondchordal group in the outbound direction on the West port 214 canlikewise include five (5) fibers, namely, fiber #8 (out), fiber #9(out), fiber #10 (out), fiber #11 (out), and fiber #12 (out) (see FIG. 3c).

As shown in FIG. 3 b, fiber #1 (in) can be used in conjunction withfiber #1 (out) to implement an optical supervisory control (OSC) channelcorresponding to the drop module 302 and the add module 310. Fiber #1(in) and fiber #1 (out) (see FIG. 3 b) can also be used in conjunctionwith the drop module 304 (such as a 4-channel DMUX filter) and the addmodule 308 (such as a 4-channel MUX filter), respectively, to implementone (1) hop connection(s) for wavelength channels 1, 2, 3, 4 (see FIG. 3b).

Likewise, as shown in FIG. 3 c, fiber #7 (in) can be used in conjunctionwith fiber #7 (out) to implement an OSC channel corresponding to thedrop module 326 and the add module 320. Fiber #7 (in) and fiber #7 (out)(see FIG. 3 c) can also be used in conjunction with the drop module 324(such as a 4-channel DMUX filter) and the add module 322 (such as a4-channel MUX filter), respectively, to implement the one (1) hopconnection(s) for the wavelength channels 1, 2, 3, 4 (see FIG. 3 c).

In addition, fiber #2 (in) (see FIG. 3 b) can be used in conjunctionwith the drop module 306 (such as an 8-channel DMUX filter) to implementone (1) hop connection(s) for wavelength channels 1, 2, 3, 4, 5, 6, 7,8, and fiber #8 (in) (see FIG. 3 c) can be used in conjunction with thedrop module 328 (such as an 8-channel DMUX filter) to implement the one(1) hop connection(s) for the wavelength channels 1, 2, 3, 4, 5, 6, 7,8. The remaining fibers can be routed within the respective opticalfilter configurations 301, 303, as follows:

(1) fiber can be routed from position #3 (i.e., fiber #3 (in)) toposition #2 (i.e., fiber #2 (out)) of the multi-fiber ribbon cable (seeFIG. 3 b);

(2) fiber can be routed from position #4 (i.e., fiber #4 (in)) toposition #3 (i.e., fiber #3 (out)) of the multi-fiber ribbon cablethrough the add module 312 (such as a 2-channel MUX filter) for use withthe wavelength channels 1, 2 (see FIG. 3 b);

(3) fiber can be routed from position #5 (i.e., fiber #5 (in)) toposition #4 (i.e., fiber #4 (out)) of the multi-fiber ribbon cablethrough the add module 314 (such as a 2-channel MUX filter) for use withthe wavelength channels 3, 4 (see FIG. 3 b);

(4) fiber can be routed from position #6 (i.e., fiber #6 (in)) toposition #5 (i.e., fiber #5 (out)) of the multi-fiber ribbon cablethrough the add module 316 (such as a 2-channel MUX filter) for use withthe wavelength channels 5, 6 (see FIG. 3 b);

(5) fiber can be routed from position #6 (i.e., fiber #6 (out)) of themulti-fiber ribbon cable to the add module 318 (such as a 2-channel MUXfilter) for use with the wavelength channels 7, 8 (see FIG. 3 b);

(6) fiber can be routed from position #9 (i.e., fiber #9 (in)) toposition #8 (i.e., fiber #8 (out)) of the multi-fiber ribbon cable (seeFIG. 3 c);

(7) fiber can be routed from position #10 (i.e., fiber #10 (in)) toposition #9 (i.e., fiber #9 (out)) of the multi-fiber ribbon cablethrough the add module 330 (such as a 2-channel MUX filter) for use withthe wavelength channels 1, 2 (see FIG. 3 c);

(8) fiber can be routed from position #11 (i.e., fiber #11 (in)) toposition #10 (i.e., fiber #10 (out)) of the multi-fiber ribbon cablethrough the add module 332 (such as a 2-channel MUX filter) for use withthe wavelength channels 3, 4 (see FIG. 3 c);

(9) fiber can be routed from position #12 (i.e., fiber #12 (in)) toposition #11 (i.e., fiber #11 (out)) of the multi-fiber ribbon cablethrough the add module 334 (such as a 2-channel MUX filter) for use withthe wavelength channels 5, 6 (see FIG. 3 c); and

(10) fiber can be routed from position #12 (i.e., fiber #12 (out)) ofthe multi-fiber ribbon cable to the add module 336 (such as a 2-channelMUX filter) for use with the wavelength channels 7, 8 (see FIG. 3 c).

With reference to the first chordal group including fiber #1 (in) on theWest port 214 (see FIG. 3 b), the matching first chordal group includingfiber #1 (out) on the East port 212 (see FIG. 3 b), and optical node 1(see FIG. 4), the drop module 304 effectively drops the inboundconnection of chord 404 (see FIG. 4) from optical node 11 on wavelengths1, 2, 3, 4, and the drop module 302 drops the inbound connection of theoptical supervisory channel (OSC). Further, the add module 308 adds theoutbound connection of chord 402 destined for optical node 2 onwavelengths 1, 2, 3, 4, and the add module 310 adds the outboundconnection of the optical supervisory channel (OSC). With reference tothe second chordal group including fiber #2 (in), fiber #3 (in), fiber#4 (in), fiber #5 (in), and fiber #6 (in) on the West port 214 (see FIG.3 b), and the matching second chordal group including fiber #2 (out),fiber #3 (out), fiber #4 (out), fiber #5 (out), and fiber #6 (out) onthe East port 212 (see FIG. 3 b), the add module 318 adds wavelengths 7,8 to fiber #6 (out), and the add module 316 adds wavelengths 5, 6 tofiber #5 (out) and all other wavelengths are routed from fiber #6 (in)to fiber #5 (out). Further, the add module 314 adds wavelengths 3, 4 tofiber #4 (out) and all other wavelengths are routed from fiber #5 (in)to fiber #4 (out), and the add module 312 adds wavelengths 1, 2 to fiber#3 (out) and all other wavelengths are routed from fiber #4 (in) tofiber #3 (out). Moreover, although no wavelengths are added to fiber #2(out), all wavelengths are routed from fiber #3 (in) to fiber #2 (out).Fiber #2 (in) is terminated by the drop module 306, which dropswavelengths 1, 2, 3, 4, 5, 6, 7, 8.

With reference to the first chordal group including fiber #7 (in) on theEast port 212 (see FIG. 3 c), the matching first chordal group includingfiber #7 (out) on the West port 214 (see FIG. 3 c), and optical node 1(see FIG. 4), the drop module 324 effectively drops the inboundconnection of chord 402 (see FIG. 4) from optical node 2 on wavelengths1, 2, 3, 4, and the drop module 326 drops the inbound connection of theoptical supervisory channel (OSC). Further, the add module 322 adds theoutbound connection of chord 404 destined for optical node 11 onwavelengths 1, 2, 3, 4, and the add module 320 adds the outboundconnection of the optical supervisory channel (OSC). With reference tothe second chordal group including fiber #8 (in), fiber #9 (in), fiber#10 (in), fiber #11 (in), and fiber #12 (in) on the East port 212 (seeFIG. 3 c), and the matching second chordal group including fiber #8(out), fiber #9 (out), fiber #10 (out), fiber #11 (out), and fiber #12(out) on the West port 214 (see FIG. 3 c), the add module 336 addswavelengths 7, 8 to fiber #12 (out), and the add module 334 addswavelengths 5, 6 to fiber #11 (out) and all other wavelengths are routedfrom fiber #12 (in) to fiber #11 (out). Further, the add module 332 addswavelengths 3, 4 to fiber #10 (out) and all other wavelengths are routedfrom fiber #11 (in) to fiber #10 (out), and the add module 330 addswavelengths 1, 2 to fiber #9 (out) and all other wavelengths are routedfrom fiber #10 (in) to fiber #9 (out). Moreover, although no wavelengthsare added to fiber #8 (out), all wavelengths are routed from fiber #9(in) to fiber #8 (out). Fiber #8 (in) is terminated by the drop module328, which drops wavelengths 1, 2, 3, 4, 5, 6, 7, 8.

It is noted that, in the optical filter configurations 301, 303, therespective MUX and DMUX filters can be implemented as active or passivecomponents. It is further noted that fiber #1 (in) and the drop module304 can be used in conjunction with fiber #1 (out) and the add module308 to implement a connection path through at least the circuit switch348 (see FIG. 3 a) for the OSC channel corresponding to the drop module302 and the add module 310. Similarly, fiber #7 (in) and the drop module324 can be used in conjunction with fiber #7 (out) and the add module322 to implement a connection path through at least the circuit switch348 (see FIG. 3 a) for the OSC channel corresponding to the drop module326 and the add module 320. By implementing such connection paths forthe OSC channels through the circuit switch 348, the OSC channels can bemaintained as operational, even in the event of an optical node failure,by proper steering of signals on the respective OSC channels, by thecircuit switch 348, to bypass the failed optical node.

FIG. 4 depicts the optical ring network 100 including optical nodes 1through 11 (see also FIG. 1), illustrating the switching topology thatcan be obtained when the respective optical nodes are configured inaccordance with optical node 1 (see FIG. 2), which includes the opticalfilter configurations 301, 303 (see FIGS. 3 a, 3 b, 3 c). As shown inFIG. 4, the switching topology of the optical ring network 100 is achordal ring. As described above with reference to optical node 1, eachof optical nodes 1-11 can be connected to its neighboring optical nodeon the optical ring network 100 in the East (clockwise) and West(counter clockwise) directions using one or more multi-fiber ribboncables. It is noted that FIG. 4 depicts the switching topology betweenoptical node 1 and the respective optical nodes 2-11 only, for clarityof illustration. It should be understood, however, that the switchingtopology between each of optical nodes 2-11, and the remaining opticalnodes on the optical ring network 100, can be like the switchingtopology illustrated in FIG. 4 for optical node 1. It is further notedthat such multi-fiber ribbon cables are described herein as includingtwelve (12) optical fibers (e.g., fibers #1-#6, see FIG. 3 b; and,fibers #7-#12, see FIG. 3 c) for purposes of illustration, and that anyother suitable number of optical fibers within such multi-fiber ribboncables may be employed.

With reference to FIG. 4, a predetermined number of wavelengths, such asthe eight (8) wavelengths 1, 2, 3, 4, 5, 6, 7, 8, can be employed, inwhich the respective wavelengths may correspond to WDM channels, CWDMchannels, or DWDM channels. Further, each wavelength channel can providea 10 Gb/s optical connection between respective optical nodes, or anyother suitable optical connection. With reference to FIGS. 3 b and 3 c,four (4) wavelength channels, namely, the wavelength channelscorresponding to wavelengths 1, 2, 3, 4, are provided for use betweeneach optical node 1-11 and its neighboring optical node on the opticalring network 100 illustrated herein, and therefore a 40 Gb/s opticalconnection is provided between the neighboring optical nodes. Forexample, with regard to optical node 1, the wavelength channelscorresponding to wavelengths 1, 2, 3, 4 separated by the drop module 324from an optical signal received over fiber #7 (in) (see FIG. 3 b), andadded by the add module 308 to the optical signal provided fortransmission over fiber #1 (out) (see FIG. 3 b), can be employed toprovide a 40 Gb/s optical connection 402 between optical node 1 andoptical node 2 on fiber #1. Likewise, the wavelength channelscorresponding to wavelengths 1, 2, 3, 4 separated by the drop module 304from an optical signal received over fiber #1 (in) (see FIG. 3 c), andadded by the add module 322 to the optical signal provided fortransmission over fiber #7 (out) (see FIG. 3 c), can be employed toprovide a 40 Gb/s optical connection 404 between optical node 1 andoptical node 11 on fiber #7.

With further regard to optical node 1, a pair of wavelength channels,namely, the wavelength channels corresponding to wavelengths 1, 2 addedby the add module 312 to the optical connection path 390 (see FIG. 3 a)between fiber #4 (in) and fiber #3 (out) (see FIG. 3 b), can be employedto provide a 20 Gb/s logical connection over a chord 406 between opticalnode 1 and optical node 3. Similarly, the pair of wavelength channelscorresponding to wavelengths 1, 2 added by the add module 330 to theoptical connection path 393 (see FIG. 3 a) between fiber #10 (in) andfiber #9 (out) (see FIG. 3 c) can be employed to provide a 20 Gb/slogical connection over chords 408 between optical node 1 and opticalnode 10. Likewise, a pair of wavelength channels, namely, the wavelengthchannels corresponding to wavelengths 3, 4 added by the add module 314to the optical connection path 389 (see FIG. 3 a) between fiber #5 (in)and fiber #4 (out) (see FIG. 3 b), can be employed to provide a 20 Gb/slogical connection over chords 410 between optical node 1 and opticalnode 4. Similarly, the pair of wavelength channels corresponding towavelengths 3, 4 added by the add module 332 to the optical connectionpath 394 (see FIG. 3 a) between fiber #11 (in) and fiber #10 (out) (seeFIG. 3 c) can be employed to provide a 20 Gb/s logical connection overchords 412 between optical node 1 and optical node 9. Further, a pair ofwavelength channels, namely, the wavelength channels corresponding towavelengths 5, 6 added by the add module 316 to the optical connectionpath 388 (see FIG. 3 a) between fiber #6 (in) and fiber #5 (out) (seeFIG. 3 b), can be employed to provide a 20 Gb/s logical connection overchords 414 between optical node 1 and optical node 5. Similarly, thepair of wavelength channels corresponding to wavelengths 5, 6 added bythe add module 334 to the optical connection path 395 (see FIG. 3 a)between fiber #12 (in) and fiber #11 (out) (see FIG. 3 c) can beemployed to provide a 20 Gb/s logical connection over chords 416 betweenoptical node 1 and optical node 8. Moreover, a pair of wavelengthchannels, namely, the wavelength channels corresponding to wavelengths7, 8 added by the add module 318 to an optical signal provided to fiber#6 (out) (see FIG. 3 b), can be employed to provide a 20 Gb/s logicalconnection over chords 418 between optical node 1 and optical node 6.Similarly, the pair of wavelength channels corresponding to wavelengths7, 8 added by the add module 336 to an optical signal provided to fiber#12 (out) (see FIG. 3 b) can be employed to provide a 20 Gb/s logicalconnection over chords 420 between optical node 1 and optical node 7.

Because the optical filter configuration 301 (see FIG. 3 b) isconfigured to communicably couple fibers #3-#6 (in) to fibers #2-#5(out), respectively, selected pairs of the wavelength channels 1-8 cantraverse the respective fibers through one or more of optical nodes 2-6in the East (clockwise) direction along the optical ring network 100,until they reach fiber #2 (in) connected to the drop module 306 withinthe optical node to which a 20 Gb/s logical connection, or any othersuitable logical connection, in the East direction from optical node 1is desired. The drop module 306 can then provide the selected pairs ofwavelength channels for ultimate receipt at the circuit switch 348 (seeFIG. 3 a) for subsequent processing. Likewise, because the opticalfilter configuration 303 (see FIG. 3 c) is configured to communicablycouple fibers #9-#12 (in) with fibers #8-#11 (out), respectively,selected pairs of the wavelength channels 1-8 can traverse therespective fibers through one or more of optical nodes 7-11 in the West(counter clockwise) direction along the optical ring network 100, untilthey reach fiber #8 (in) connected to the drop module 328 within theoptical node to which a 20 Gb/s logical connection, or any othersuitable logical connection, in the West direction from optical node 1is desired. The drop module 328 can then provide the selected pairs ofwavelength channels for ultimate receipt at the circuit switch 348 (seeFIG. 3 a) for subsequent forwarding. It should be understood that suchlogical connections in the East/West directions from each of opticalnodes 2-11 on the optical ring network 100 can be established in ananalogous fashion.

It is noted that the SDM/WDM shifting channel plan illustrated in FIGS.3 b-3 c allows the same wavelength w to be reused multiple times in achordal group so long as each time after it is added onto an outputfiber k of an output chordal group, the wavelength is extracted from thematching input chordal group on an equal or lower numbered input fiber jbefore being added again within the same output chordal group on anoutput fiber m<k. If a wavelength w is added on the output fiber k andnext dropped on the input fiber j≦k, and if optical nodes implementingidentical channel plans are cabled in a path or ring of sufficientlength, then w will carry an optical connection that optically bypassesk−j optical nodes, producing a chord of length k−j+1. For example, withreference to FIG. 3 b, wavelengths 7, 8 are added to fiber #6 (out),which is the fifth fiber of the outbound chordal group including fiber#2 (out), fiber #3 (out), fiber #4 (out), fiber #5 (out), and fiber #6(out). Wavelengths 7, 8 are dropped on fiber #2 (in), which is the firstfiber of the matching inbound chordal group including fiber #2 (in),fiber #3 (in), fiber #4 (in), fiber #5 (in), and fiber #6 (in).Accordingly, if optical nodes implementing an identical channel plan areconnected in a path or ring of sufficient length, then wavelengths 7, 8can carry an optical connection that optically bypasses four otheroptical nodes, producing a chord of length 5.

It is further noted that a chordal ring network with N optical nodes,numbered n=0, 1, 2, . . . N−1, can have chords of lengths r₁, r₂, . . .r_(C), such that each optical node n is connected to its neighboringoptical nodes n+r_(c) (mod N) and n−r_(c) (mod N) with a multiplicity ofs_(c)≧1 chords (c=1 . . . C), each chord representing an uplink. Theswitching topology for such a chordal ring network can be denoted asR_(N)(r₁ ^(s) ¹ ; r₂ ^(s) ² ; r₃ ^(s) ³ ; . . . ; r_(C) ^(s) ^(C) ). TheSDM/WDM shifting channel plan illustrated in FIGS. 3 b-3 c can be usedto implement a switching topology denoted as R₁₁(1⁴; 2²; 3²; 4²;5^(2;)). In general, an SDM/WDM shifting channel plan in accordance withFIGS. 3 b-3 c can implement a switching topology denoted as R_(N)(1⁴;2²; 3²; 4²; 5²;) for any N, in which, for N<6, some or all of the chordsmay terminate or pass through their source optical nodes, and, for N>11,a regular chordal ring can be created that is not full mesh.

FIG. 5 depicts an illustrative embodiment of an exemplary opticalchordal ring network 500 that includes a plurality of optical nodes 1through 20, each configured in accordance with optical node 1 (see FIGS.2, 3 a, 3 b, 3 c). Each of optical nodes 1-20 can be connected to itsneighboring optical node on the optical chordal ring network 500 (seeFIG. 5) in the East (clockwise) and West (counter clockwise) directionsusing one or more multi-fiber ribbon cables. It is noted that FIG. 5depicts the switching topology between optical node 1 and the respectiveoptical nodes 2-6 and 16-20 only, for clarity of illustration. It shouldbe understood, however, that the switching topology between each ofoptical nodes 2-20, and the remaining optical nodes on the opticalchordal ring network 500, can be like the switching topology illustratedin FIG. 5 for optical node 1.

With reference to FIG. 5, a predetermined number of wavelengths, such asthe eight (8) wavelengths 1, 2, 3, 4, 5, 6, 7, 8, can be employed, inwhich the respective wavelengths may correspond to WDM channels, CWDMchannels, or DWDM channels. Further, each wavelength channel can providea 10 Gb/s optical connection between respective optical nodes, or anyother suitable optical connection. Four (4) wavelength channels, namely,the wavelength channels corresponding to wavelengths 1, 2, 3, 4, areprovided for use between each optical node 1-20 and its neighboringoptical node on the optical chordal ring network 500, and therefore a 40Gb/s optical connection is provided between the neighboring opticalnodes. For example, with regard to optical node 1, the wavelengthchannels corresponding to wavelengths 1, 2, 3, 4 can be employed toprovide a 40 Gb/s optical connection 502 between optical node 1 andoptical node 2, and a 40 Gb/s optical connection 504 between opticalnode 1 and optical node 20. With further regard to optical node 1, two(2) wavelength channels, namely, wavelength channels corresponding towavelengths 1, 2, can be employed to provide a 20 Gb/s logicalconnection over chords 506 between optical node 1 and optical node 3,and a 20 Gb/s logical connection over chords 508 between optical node 1and optical node 19; two (2) wavelength channels, namely, wavelengthchannels corresponding to wavelengths 3, 4, can be employed to provide a20 Gb/s logical connection over chords 510 between optical node 1 andoptical node 4, and a 20 Gb/s logical connection over chords 512 betweenoptical node 1 and optical node 18; two (2) wavelength channels, namely,wavelength channels corresponding to wavelengths 5, 6, can be employedto provide a 20 Gb/s logical connection over chords 514 between opticalnode 1 and optical node 5, and a 20 Gb/s logical connection over chords516 between optical node 1 and optical node 17; and, two (2) wavelengthchannels, namely, wavelength channels corresponding to wavelengths 7, 8,can be employed to provide a 20 Gb/s logical connection over chords 518between optical node 1 and optical node 6, and a 20 Gb/s logicalconnection over chords 520 between optical node 1 and optical node 16.

FIG. 6 depicts an exemplary simplified switch module 609 that can beused to illustrate how an optical node, such as optical node 1 (seeFIGS. 2, 3 a), can be configured to support low latency multicast and/orbroadcast data channels. As shown in FIG. 6, the switch module 609includes a packet switch 646, a plurality of input/output transceivers602.1-602.2, and circuit switches 648 disposed between the packet switch646 and the plurality of input/output transceivers 602.1-602.2. Forexample, the input/output transceiver 602.1 (such as an XFP or SFP+transceiver) can be communicably connected to one or more opticalconnection paths in the West (counter clockwise) direction along anoptical ring network. Further, the input/output transceiver 602.2 (suchas an XFP or SFP+ transceiver) can be communicably connected to one ormore optical connection paths in the East (clockwise) direction alongthe optical ring network. The circuit switches 648 include a pair ofcircuit switches 603.1, 603.2. It is noted that clock and data recovery(CDR) may be implemented, as required and/or as desired, either as anintegrated part of the circuit switches 603.1, 603.2, or externally.

With reference to FIG. 6, the circuit switches 603.1, 603.2 are eachconfigured with integrated CDR capability. As shown in FIG. 6, a“receive” (Rx) output of the input/output transceiver 602.1 is connectedto an IN1 input of the circuit switch 603.1, and an Rx output of theinput/output transceiver 602.2 is connected to an IN1 input of thecircuit switch 603.2. Further, an OUT1 output of the circuit switch603.1 is connected to a “transmit” (Tx) input of the input/outputtransceiver 602.2, and an OUT1 output of the circuit switch 603.2 isconnected to a Tx input of the input/output transceiver 602.1. Moreover,an OUT2 output of the circuit switch 603.1 is connected to an IN1 inputof the packet switch 646, and an OUT2 output of the circuit switch 603.2is connected to an IN2 input of the packet switch 646. In addition, anOUT1 output of the packet switch 646 is connected to an IN2 input of thecircuit switch 603.2, and an OUT2 output of the packet switch 646 isconnected to an IN2 input of the circuit switch 603.1.

To receive an optical signal on a broadcast data channel from the Westdirection along an optical ring network, the input/output transceiver602.1 can receive the optical signal, convert the optical signal toelectrical form, and send the electrical signal through its Rx output tothe IN1 input of the circuit switch 603.1. The circuit switch 603.1, inturn, can send the electrical signal through its OUT2 output to the IN1input of the packet switch 646, and through its OUT1 output to the Txinput of the input/output transceiver 602.2. The input/outputtransceiver 602.2 can then convert the electrical signal back to opticalform, and relay the optical signal to a downstream node, in the East(clockwise) direction along the optical ring network, with low latency.

Similarly, to receive an optical signal on a broadcast data channel fromthe East direction along an optical ring network, the input/outputtransceiver 602.2 can receive the optical signal, convert the opticalsignal to electrical form, and send the electrical signal through its Rxoutput to the IN1 input of the circuit switch 603.2. The circuit switch603.2, in turn, can send the electrical signal through its OUT2 outputto the IN2 input of the packet switch 646, and through its OUT1 outputto the Tx input of the input/output transceiver 602.1. The input/outputtransceiver 602.1 can then convert the electrical signal back to opticalform, and relay the optical signal to a downstream node, in the West(counter clockwise) direction along the optical ring network, with lowlatency.

To receive an optical signal on a multicast data channel from the Westdirection along an optical ring network, the input/output transceiver602.1 can receive the optical signal, convert the optical signal toelectrical form, and send the electrical signal through its Rx output tothe IN1 input of the circuit switch 603.1. The circuit switch 603.1, inturn, can send the electrical signal through its OUT2 output to the IN1input of the packet switch 646, as required to achieve the desiredmulticast functionality. The circuit switch 603.1 can also send theelectrical signal through its OUT1 output to the Tx input of theinput/output transceiver 602.2. The input/output transceiver 602.2 canthen convert the electrical signal back to optical form, and relay theoptical signal to a downstream node, in the East (clockwise) directionalong the optical ring network, with low latency. It is noted that theswitch module 609 can be employed to receive an optical signal on amulticast data channel from the East direction along the optical ringnetwork in an analogous fashion.

It is further noted that low latency multicast/broadcast functionalitycan be crucial in certain applications/services, such as medicalapplications and financial services applications. Such low latencymulticast/broadcast functionality can be achieved by configuring circuitswitches of a plurality of optical nodes to establish a single duplexconnection from a source or origin Ethernet switch to a primarydestination Ethernet switch or the source Ethernet switch itself, usinga plurality of the source Ethernet switch's uplink ports and simplexconnections from the same source Ethernet switch and uplink ports to aplurality of secondary Ethernet switches uplink ports, with one or morecircuit switches establishing a simplex multicast or broadcastconnection from one or more of its input ports to a plurality of itsoutput ports, thereby enabling data multicasting and broadcasting from aserver or servers connected to the source Ethernet switch to a pluralityof servers connected to the same Ethernet switch and/or differentEthernet switches. In one embodiment, transmitting uplink ports on thesecondary set of destination Ethernet switches are muted. In anotherembodiment, the transmitting uplink ports on the secondary set ofdestination Ethernet switches are not muted, but data transmission isdisabled by the circuit switches connected to the secondary transmittinguplink ports. In a further embodiment, the transmitting uplink ports onone or more of the secondary Ethernet switches are enabled and employedin separate multicast or broadcast communications. The plurality ofoptical nodes can be communicably coupled on an optical ring network,such that one of the destination Ethernet switches is the sourceEthernet switch, and an outbound signal from an uplink of the sourceEthernet switch is routed through the network, for example, by routingthe outbound signal around the ring so that it connects back on thesource Ethernet switch to establish the duplex connection. For example,in a physical ring network, a duplex connection can be established fromthe source Ethernet switch uplink port to itself (using the circuitswitch), and the outbound signal can be dropped at a plurality ofintermediate Ethernet switches to establish multicast or broadcastsimplex communications from the source Ethernet switch to thedestination Ethernet switches.

FIG. 7 a depicts an exemplary optical ring network 700, including aplurality of optical nodes 701, 702, 703, 704 configured to support alow latency multicast data channel on the optical ring network 700. Asshown in FIG. 7 a, optical node 701 includes a circuit switch 706 and apacket switch 708, optical node 702 includes a circuit switch 710 and apacket switch 712, optical node 703 includes a circuit switch 714 and apacket switch 716, and optical node 704 includes a circuit switch 718and a packet switch 720. For example, each of the circuit switches 706,710, 714, 718 can operate in accordance with the exemplary functionalityof the circuit switches 648 (see FIG. 6), and therefore the circuitswitches 706, 710, 714, 718 can each be configured with integrated CDRcapability. Further, each of the packet switches 708, 712, 716, 720 canoperate in accordance with the exemplary functionality of the packetswitch 646 (see FIG. 6). With reference to FIG. 7 a, one of the opticalnodes, such as optical node 701, can be designated as a multicast masternode, and some or all of the remaining optical nodes, such as opticalnodes 702, 703, 704, can each be designated as a slave node. To achievethe desired low latency multicast/broadcast functionality, one or moreof the designated slave nodes (e.g., optical nodes 702, 703, and/or 704)can be communicably coupled to the designated multicast master node(e.g., optical node 701). In addition, optical (multicast master) node701 and optical (slave) nodes 702, 703, 704 are communicably coupled toexternal computerized devices 750, 752, 754, 756, respectively. Some ofthe external computerized devices, such as the external computerizeddevices 754, 756, can each be designated as a multicast/broadcastsubscriber.

The multicast master node, such as optical node 701, can be configuredto include a loopback interface to assure that there is always at leastone active interface, and that link has been established on themulticast master node. More specifically, in order for a transmitterport of the optical (multicast master) node 701 to be able to transmitin an Ethernet switched network, link must first be established. Theterm “link” in this context means that the receive side of the port isreceiving valid information from the transmitter, and the requirementsof the physical (phy) level are met. The transmitter may be on themulticast master (e.g., in loopback) or any other paired port. Ifanother paired port is used to establish link with the multicast master,then that port must also establish link by having valid data transmittedto its receiver required to establish link. For example, this data maycorrespond to the output of the multicast master.

It is noted that the data from the multicast master is unidirectional innature. If a port other than a port on the multicast master is used toestablish link with the multicast master port, then this does not implythat there cannot be bidirectional traffic between the multicast masterand the other port. In this case, all other receivers will be onlyreceiving the data, and not participating in bidirectionalcommunication. It is further noted that the data received at themulticast master is primarily used to establish link, but this does notpreclude other uses.

In a static configuration (e.g., standard Ethernet protocol), forexample, spanning tree protocol could be disabled on multicast masterports, and any bridge loops would have to be prevented. The forwardingtable of the packet switch hosting the multicast master may be populatedwith destination MAC addresses, source MAC addresses, incoming portinformation, VLAN information, multicast addresses, or any othersuitable information, which are to be forwarded to the multicast masterport, typically using a command line interface (CLI). These destinationMAC addresses may be unicast, multicast, or broadcast. On the packetswitch(es) hosting the receiver port, the receiver port is physicallyconnected to the multicast master. The forwarding table, on thereceiving packet switch, may be populated with destination MACaddresses, source MAC addresses, incoming port information, VLANinformation, multicast addresses, or any other suitable information, forforwarding the received Ethernet frames to any, many, or all of theother ports on the packet switch. It is noted that the Ethernet framesinclude packet header fields that can be used to generate an output portmapping. In one embodiment, the packet switch 708 on the multicastmaster corresponds to the transmitter, and the packet switches 712, 716,720, configured by the circuit switches 710, 714, 718, respectively,correspond to the receivers. Further, the circuit switch 706 on themulticast master is configured to loopback to the receiver port of themulticast master to establish link.

Accordingly, to achieve a low latency multicast data channel on theoptical ring network 700 (see FIG. 7 a), the packet switch 708 includedin optical (multicast master) node 701 can provide one or more signals,in electrical form, to the circuit switch 706 within optical (multicastmaster) node 701, for subsequent conversion to optical form and additionto the multicast data channel. Optical (multicast master) node 701 canthen send the signals on the multicast data channel in the East(clockwise) direction along the optical ring network 700, allowing thesignals to be received at the circuit switch 710 included in optical(slave) node 702. Because, in this example, the external computerizeddevice 752 coupled to optical (slave) node 702 is not a multicastsubscriber, optical (slave) node 702 can be regarded as not being anintended recipient of the signals. Optical (slave) node 702 forwards thesignals, with low latency, on the multicast data channel in the East(clockwise) direction for receipt at the circuit switch 714 included inoptical (slave) node 703, and blocks the signals from reaching thepacket switch 712. Because, in this example, the external computerizeddevice 754 coupled to optical (slave) node 703 is a multicastsubscriber, optical (slave) node 703 can be regarded as an intendedrecipient of the signals. The circuit switch 714 provides the signals,separated from the multicast data channel, to the packet switch 716within optical (slave) node 703 for subsequent forwarding to theexternal computerized (subscriber) device 754. Optical (slave) node 703also forwards the signals, with low latency, on the multicast datachannel in the East (clockwise) direction for receipt at the circuitswitch 718 included in optical (slave) node 704. Because, in thisexample, the external computerized device 756 coupled to optical (slave)node 704 is also a multicast subscriber, optical (slave) node 704 canlikewise be regarded as an intended recipient of the signals. Thecircuit switch 718 provides the signals, separated from the multicastdata channel, to the packet switch 720 within optical (slave) node 704for subsequent forwarding to the external computerized (subscriber)device 756. Optical (slave) node 704 then forwards the signals, with lowlatency, on the multicast data channel in the East (clockwise) directionfor receipt at the circuit switch 706 included in optical (multicastmaster) node 701. It is noted that optical (slave) nodes 702, 703, 704can each forward the optical signals on the multicast data channel to adownstream node on the optical ring network 700, without first requiringthe signals to pass through the packet switch included in the respectiveoptical node. For example, following optical-to-electrical (O-E)conversion of the optical signals, optical (slave) nodes 702, 703, 704can prevent the electrical signals from reaching the packet switches712, 716, 720, respectively. It is further noted that the plurality ofoptical nodes 701, 702, 703, 704 can be configured to support such a lowlatency multicast data channel for sending optical signals in the West(counter clockwise) direction along the optical ring network 700.

FIG. 7 b depicts the optical ring network 700 that includes theplurality of optical nodes 701, 702, 703, 704, which are configured tosupport a low latency broadcast data channel on the optical ring network700. With reference to FIG. 7 b, optical node 701 is again designated asa multicast master node, and optical nodes 702, 703, 704 are againdesignated as respective slave nodes. Further, the external computerizeddevices 750, 752, 754, 756 are each designated as a broadcastsubscriber. To achieve a low latency broadcast data channel on theoptical ring network 700 (see FIG. 7 b), the packet switch 708 includedin optical (multicast master) node 701 can provide one or more signals,in electrical form, to the circuit switch 706 within optical (multicastmaster) node 701, for subsequent conversion to optical form and additionto the broadcast data channel. Optical (multicast master) node 701 canthen send the signals on the broadcast data channel in the East(clockwise) direction along the optical ring network 700, allowing thesignals to be received at the circuit switch 710 included in optical(slave) node 702. The circuit switch 710 provides the signals, separatedfrom the broadcast data channel, to the packet switch 712 within optical(slave) node 702 for subsequent forwarding to the external computerized(subscriber) device 752. Further, optical (slave) node 702 forwards thesignals, with low latency, on the broadcast data channel in the East(clockwise) direction for receipt at the circuit switch 714 included inoptical (slave) node 703. The circuit switch 714 provides the signals,separated from the broadcast data channel, to the packet switch 716within optical (slave) node 703 for subsequent forwarding to theexternal computerized (subscriber) device 754. Optical (slave) node 703also forwards the signals, with low latency, on the broadcast datachannel in the East (clockwise) direction for receipt at the circuitswitch 718 included in optical (slave) node 704. The circuit switch 718provides the signals, separated from the broadcast data channel, to thepacket switch 720 within optical (slave) node 704 for subsequentforwarding to the external computerized (subscriber) device 756. Optical(slave) node 704 then forwards the signals, with low latency, on thebroadcast data channel in the East (clockwise) direction for receipt atthe circuit switch 706 included in optical (multicast master) node 701.It is noted that optical (slave) nodes 702, 703, 704 can each forwardthe signals on the broadcast data channel to a downstream node on theoptical ring network 700, without first requiring the signals to passthrough the packet switch included in the respective optical node. It isfurther noted that the plurality of optical nodes 701, 702, 703, 704 canbe configured to support such a low latency broadcast data channel forsending optical signals in the West (counter clockwise) direction alongthe optical ring network 700.

FIG. 7 c depicts the optical ring network 700 that includes theplurality of optical nodes 701, 702, 703, 704, which are configured tosupport what is referred to herein as a “flyway channel” between aselected pair of optical nodes on the optical ring network 700. Withreference to FIG. 7 c, optical nodes 701 and 704 are designated aspaired optical nodes. It is noted that any other pair of optical nodeson the optical ring network 700 may alternatively be designated aspaired optical nodes. To employ a flyway channel on the optical ringnetwork 700 (see FIG. 7 c), the packet switch 708 included in optical(paired) node 701 can provide one or more signals, in electrical form,to the circuit switch 706 within optical (paired) node 701, forsubsequent conversion to optical form and addition to the flywaychannel. Optical (paired) node 701 can then send the signals on theflyway channel in the East (clockwise) direction along the optical ringnetwork 700, allowing the signals to be received at the circuit switch710 included in optical node 702. Because optical node 702 is not one ofthe paired optical nodes, optical node 702 can be regarded as not beingan intended recipient of the signals. Optical node 702 forwards thesignals, with low latency, on the flyway channel in the East (clockwise)direction for receipt at the circuit switch 714 included in optical node703, and blocks the signals from reaching the packet switch 712. Becauseoptical node 703 is also not one of the paired optical nodes, opticalnode 703 can likewise be regarded as not being an intended recipient ofthe signals. Optical node 703 forwards the signals, with low latency, onthe flyway channel in the East (clockwise) direction for receipt at thecircuit switch 718 included in optical (paired) node 704, and blocks thesignals from reaching the packet switch 716. Because optical node 704 isdesignated as one of the paired optical nodes, it can be regarded as anintended recipient of the signals. The circuit switch 718 provides thesignals, separated from the flyway channel, to the packet switch 720within optical (paired) node 704 for subsequent forwarding to theexternal computerized device 756, or, alternatively, the signal may beprovided to a user connection port that is configured for direct attach.It is noted that optical nodes 702, 703 can each forward the signals onthe flyway channel to a downstream node on the optical ring network 700,without first requiring the signals to pass through the packet switchincluded in the respective optical node. It is further noted that theplurality of optical nodes 701, 702, 703, 704 can be configured tosupport such a flyway channel for sending optical signals in the West(counter clockwise) direction along the optical ring network 700.

An illustrative method of providing low latency multicast/broadcastfunctionality on an optical ring network is described below withreference to FIG. 8. As depicted in step 802, multicast/broadcasttraffic is received at at least one input of an optical node on theoptical ring network. As depicted in step 804, the multicast/broadcasttraffic is converted, by an input transceiver within the optical node,from optical form to electrical form. As depicted in step 806, themulticast/broadcast traffic, in electrical form, is provided, by theinput transceiver, to a circuit switch within the optical node. Asdepicted in step 808, the multicast/broadcast traffic, in electricalform, is forwarded, at least at some times by the circuit switch, to apacket switch within the optical node for subsequent forwarding to anexternal computerized device. As depicted in step 810, themulticast/broadcast traffic, in electrical form, is forwarded, at leastat some other times by the circuit switch, to an output transceiverwithin the optical node, without first requiring the multicast/broadcasttraffic to pass through the packet switch, thereby reducing signaltransport latency within the optical node. As depicted in step 812, themulticast/broadcast traffic forwarded to the output transceiver isconverted, by the output transceiver, from electrical form to opticalform. As depicted in step 814, the multicast/broadcast traffic isforwarded, in optical form by the output transceiver, for subsequentreceipt at an optical output of the optical node on the optical ringnetwork. Because, in accordance with the illustrative method of FIG. 8,the optical node can provide such multicast/broadcast traffic, via thecircuit switch, to a downstream node on the optical ring network,without first requiring the multicast/broadcast traffic to pass throughthe packet switch, the optical node can support a multicast and/orbroadcast data channel on the optical ring network with low latency. Itis noted that the optical node can provide such data traffic on amulticast data channel, or a flyway channel, to a downstream node viaoptical connection paths communicably coupling respective inputs andrespective outputs of the optical node, without first requiring the datatraffic to pass through the circuit switch or the packet switch withinthe optical node, thereby further reducing latency within the opticalring network.

Having described the above illustrative embodiments of the presentlydisclosed data center network architectures, systems, and methods, otherembodiments or variations may be made. For example, it was describedabove that an optical ring network can be provided that includes aplurality of optical nodes interconnected by one or more multi-fiberribbon cables, in which some or all of the optical nodes are eachconfigured in accordance with optical node 1 of FIG. 2. Such opticalnodes can also be employed to implement any other suitable logicaloptical network topology.

FIG. 9 a depicts an illustrative embodiment of an optical torus network900 that includes a plurality of optical nodes 1_1 through 1_11; 2_1through 2_11; . . . ; and, 11_1 through 11_11. As shown in FIG. 9 a, oneor more multi-fiber ribbon cables may be employed as optical links tointerconnect the eleven (11) optical nodes in each row of the opticaltorus network 900, thereby forming eleven (11) optical ring networkscorresponding to the respective rows, such as optical ring networks 902,904, 906, 908. Further, one or more multi-fiber ribbon cables may beemployed to interconnect the eleven (11) optical nodes in each column ofthe optical torus network 900, thereby forming eleven (11) optical ringnetworks corresponding to the respective columns, such as optical ringnetworks 910, 912, 914, 916. It is noted that the respective rows andthe respective columns of the optical torus network 900 mayalternatively include any other suitable number of optical nodes.

FIG. 9 b depicts an exemplary configuration of optical node 1_1 on theoptical torus network 900 (see FIG. 9 a). It is noted that the otheroptical nodes 1_2 through 1_11; 2_1 through 2_11; . . . ; and, 11_1through 11_11 on the optical torus network 900 can have a configurationlike that of optical node 1_1. As shown in FIG. 9 b, optical node 1_1 isan optical node of degree-4 that includes two paired optical ports 946,944 referred to herein as the East port 946 and the West port 944, andtwo paired optical ports 940, 942 referred to herein as the North port940 and the South port 942. Optical node 1_1 also includes an opticalMUX/DMUX module 920, an optical MUX/DMUX module 936, a switch module932, and an optical backplane with a twenty-four (24) fiber connector930 and a twenty-four (24) fiber connector 938, such as HBMT™ connectorsor any other suitable connectors. Optical node 1_1 further includes afirst bundle 934 of 12 optical fibers connected between the opticalMUX/DMUX module 920 and the connector 930 in the East direction (e.g.,from optical node 1_1 toward optical node 2_1; see FIG. 9 a), a secondbundle 924 of 12 optical fibers connected between the optical MUX/DMUXmodule 920 and the connector 930 in the West direction (e.g., fromoptical node 1_1 toward optical node 11_1; see FIG. 9 a), a third bundle925 of 12 optical fibers connected between the optical MUX/DMUX module936 and the connector 938 in the North direction (e.g., from opticalnode 1_1 toward optical node 1_11; see FIG. 9 a), and a fourth bundle935 of 12 optical fibers connected between the optical MUX/DMUX module936 and the connector 938 in the South direction (e.g., from opticalnode 1_1 toward optical node 1_2; see FIG. 9 a). It is noted that theoptical MUX/DMUX modules 920, 936 can each include optical filterconfigurations that implement a hybrid SDM/WDM shifting channel planlike that implemented by the optical filter configurations 301, 303 (seeFIGS. 3 a-3 c) included in the optical MUX/DMUX module 202 (see FIG. 2).It is noted that each of the remaining optical nodes included in theoptical torus network 900 can be configured to provide input/outputcapabilities like those provided by optical node 1_1. Further,multi-fiber ribbon cables including twelve (12) optical fibers (e.g.,Fibers #1-#12; see FIGS. 3 a-3 c), or any other suitable number offibers, can be used to link the optical nodes on the respective opticalring networks (e.g., the optical ring networks 902, 904, 906, 908, 910,912, 914, 916) of FIG. 9 a.

The optical ring networks corresponding to the respective rows andcolumns of the optical torus network 900 (see FIG. 9 a) form a topologythat allows up to three (3) hop connection(s) from any externalcomputerized device connected to optical nodes 1_1 through 1_11; 2_1through 2_11; . . . ; and, 11_1 through 11_11, to any other externalcomputerized device connected to optical nodes 1_1 through 1_11; 2_1through 2_11; . . . ; and, 11_1 through 11_11, so long as sufficientbandwidth is available on the optical links interconnecting therespective optical nodes, without requiring the use of flyways ordedicated flyways. It is further noted that the topology can be extendedto achieve higher dimensions by increasing the number of opticalconnection paths within the optical nodes to accommodate an increasednumber of optical fibers in the multi-fiber ribbon cables. In general,“n” optical connection paths within the respective optical nodes,accommodating “n” optical fibers in the respective multi-fiber ribboncables, can be used to achieve an n-dimensional topology. To obtain fulllogical mesh connectivity along the rows and columns of such ann-dimensional topology, a total of m^(n) optical nodes may be employed,in which “m” corresponds to the chordal diameter in each dimension(e.g., m=11; see FIG. 9).

FIG. 9 c depicts an illustrative embodiment of a chordal path 950 formedby a plurality of optical nodes 952 of degree-2 connected to one anotherin a line between a pair of optical nodes 954, 956 of degree-1. It isnoted that the physical topology of the chordal path 950 is a path,whereas the switching topology of the chordal path 950 is a chordal pathnetwork. As shown in FIG. 9 c, the optical nodes 954, 956 of degree-1form the endpoints of the chordal path 950. Each of the optical nodes954, 956 of degree-1 can terminate, on its sole optical port, eachoptical fiber interconnecting the optical node of degree-1 with itsneighboring optical node of degree-2 on the chordal path 950.

FIG. 9 d depicts an illustrative embodiment of a Manhattan Streetphysical topology 960 that includes a plurality of optical nodes 962,963, 964, 965 of degree-2, a plurality of optical nodes 966 of degree-3connected along the row between optical nodes 962, 963, a plurality ofoptical nodes 967 of degree-3 connected along the column between opticalnodes 963, 964, a plurality of optical nodes 968 of degree-3 connectedalong the row between optical nodes 964, 965, and a plurality of opticalnodes 969 of degree-3 connected along the column between optical nodes965, 962. For example, such an optical node of degree-3 can have a Westport and an East port that are paired optical ports, and a South portthat is a terminal port for terminating all of the wavelengths on all ofthe fibers of a South port/North port channel plan. As illustrated inFIG. 9 d, the remaining optical nodes (not numbered) in the interior ofthe Manhattan Street physical topology 960 are optical nodes ofdegree-4. The optical nodes of degree-4 are logically laid out in theManhattan Street physical topology 960 with each optical node connectedto its four neighboring optical nodes through its East, West, North, andSouth ports with a multitude of fibers, in which the first optical nodeand the last optical node in a row, and the first optical node and thelast optical node in a column, have terminal ports that terminate asuitable channel plan.

More specifically, optical node 962 has an East port connected tooptical node 972 and a South port connected to optical node 979, opticalnode 963 has a West port connected to optical node 973 and a South portconnected to optical node 974, optical node 965 has an East portconnected to optical node 977 and a North port connected to optical node978, and optical node 964 has a West port connected to optical node 976and a North port connected to optical node 975. Further, optical nodes966 each have paired East and West ports connected to their neighboringoptical nodes in the East and West directions, respectively, and a Southport connected to their neighboring optical nodes in the Southdirection, optical nodes 967 each have paired North and South portsconnected to their neighboring optical nodes in the North and Southdirections, respectively, and a West port connected to their neighboringoptical nodes in the West direction, optical nodes 968 each have pairedEast and West ports connected to their neighboring optical nodes in theEast and West directions, respectively, and a North port connected totheir neighboring optical nodes in the North direction, and opticalnodes 969 each have paired North and South ports connected to theirneighboring optical nodes in the North and South directions,respectively, and an East port connected to their neighboring opticalnodes in the East direction. All of the remaining optical nodes (notnumbered) in the interior of the Manhattan Street physical topology 960have paired East and West ports connected to their neighboring opticalnodes in the East and West directions, respectively, and paired Northand South ports connected to their neighboring optical nodes in theNorth and South directions, respectively.

It was also described above that the pair of optical configurations 301,303 (see FIGS. 3 a, 3 b, 3 c) included in the optical MUX/DMUX module202 may be employed to implement a hybrid SDM/WDM shifting channel plan.To increase the bandwidth of the optical connection paths betweenoptical nodes, without requiring an increased number of wavelengthchannels, exemplary optical configurations 1001, 1003 (see FIGS. 10 a,10 b) may be employed in place of the optical configurations 301, 303,respectively, within the optical MUX/DMUX module 202.

With regard to the optical configuration 1001 of FIG. 10 a, fiber #1(in) can be used in conjunction with fiber #1 (out) to implement an OSCchannel corresponding to a drop module 1002 and an add module 1010.Fiber #1 (in) and fiber #1 (out) (see FIG. 10 a) can also be used inconjunction with a drop module 1004 (such as a 6-channel DMUX filter)and an add module 1008 (such as a 6-channel MUX filter), respectively,to implement one (1) hop connection(s) for wavelength channels 1, 2, 3,4, 5, 6 (see FIG. 10 a). Similarly, as shown in FIG. 10 b, fiber #7 (in)can be used in conjunction with fiber #7 (out) to implement an OSCchannel corresponding to a drop module 1030 and an add module 1018.Fiber #7 (in) and fiber #7 (out) (see FIG. 10 b) can also be used inconjunction with a drop module 1028 (such as a 6-channel DMUX filter)and an add module 1020 (such as a 6-channel MUX filter), respectively,to implement the one (1) hop connection(s) for the wavelength channels1, 2, 3, 4, 5, 6 (see FIG. 10 b).

In addition, fiber #2 (in) (see FIG. 10 a) can be used in conjunctionwith a drop module 1006 (such as a 6-channel DMUX filter) to implementone (1) hop connection(s) for wavelength channels 3, 4, 5, 6, 7, 8, andfiber #8 (in) (see FIG. 10 b) can be used in conjunction with a dropmodule 1032 (such as an 6-channel DMUX filter) to implement the one (1)hop connection(s) for the wavelength channels 3, 4, 5, 6, 7, 8. Theremaining fibers can be routed within the respective opticalconfigurations 1001, 1003, as follows:

(1) fiber can be routed from position #3 (i.e., fiber #3 (in)) toposition #2 (i.e., fiber #2 (out)) of the multi-fiber ribbon cablethrough a drop module 1012 (such as a 2-channel DMUX filter) for usewith the wavelength channels 1, 2 (see FIG. 10 a);

(2) fiber can be routed from position #4 (i.e., fiber #4 (in)) toposition #3 (i.e., fiber #3 (out)) of the multi-fiber ribbon cable (seeFIG. 10 a);

(3) fiber can be routed from position #5 (i.e., fiber #5 (in)) toposition #4 (i.e., fiber #4 (out)) of the multi-fiber ribbon cablethrough a drop/add module 1014 (such as a 2-channel DMUXfilter/2-channel MUX filter) for use with the wavelength channels 3, 4(see FIG. 10 a);

(4) fiber can be routed from position #6 (i.e., fiber #6 (in)) toposition #5 (i.e., fiber #5 (out)) of the multi-fiber ribbon cable (seeFIG. 10 a);

(5) fiber can be routed from position #6 (i.e., fiber #6 (out)) of themulti-fiber ribbon cable to an add module 1016 (such as an 8-channel MUXfilter) for use with the wavelength channels 1, 2, 3, 4, 5, 6, 7, 8 (seeFIG. 10 a);

(6) fiber can be routed from position #9 (i.e., fiber #9 (in)) toposition #8 (i.e., fiber #8 (out)) of the multi-fiber ribbon cablethrough a drop module 1022 (such as a 2-channel drop module) for usewith the wavelength channels 1, 2 (see FIG. 10 b);

(7) fiber can be routed from position #10 (i.e., fiber #10 (in)) toposition #9 (i.e., fiber #9 (out)) of the multi-fiber ribbon cable (seeFIG. 10 b);

(8) fiber can be routed from position #11 (i.e., fiber #11 (in)) toposition #10 (i.e., fiber #10 (out)) of the multi-fiber ribbon cablethrough a drop/add module 1024 (such as a 2-channel DMUXfilter/2-channel MUX filter) for use with the wavelength channels 3, 4(see FIG. 10 b);

(9) fiber can be routed from position #12 (i.e., fiber #12 (in)) toposition #11 (i.e., fiber #11 (out)) of the multi-fiber ribbon cable(see FIG. 10 b); and

(10) fiber can be routed from position #12 (i.e., fiber #12 (out)) ofthe multi-fiber ribbon cable to an add module 1026 (such as a 8-channelMUX filter) for use with the wavelength channels 1, 2, 3, 4, 5, 6, 7, 8(see FIG. 10 b).

It is noted that, in the optical configurations 1001, 1003, therespective MUX and DMUX filters can be implemented as active or passivecomponents.

It was further described above with regard to the optical filterconfiguration 301 (see FIG. 3 a, 3 b) that fiber #1 (in) can be used inconjunction with the drop module 304, and fiber #1 (out) can be used inconjunction with the add module 308, to implement one (1) hopconnection(s) for the wavelength channels 1, 2, 3, 4, but withoutproviding a direct connection between fiber #1 (in) and fiber #1 (out)within the optical MUX/DMUX module 202 (see FIGS. 2, 3 a). To providesuch a direct connection between fiber #1 (in) and fiber #1 (out) withinthe optical MUX/DMUX module 202, an optical filter configuration 1101(see FIG. 11) may be employed in place of the optical filterconfiguration 301. As shown in FIG. 11, the optical filter configuration1101 is like the optical filter configuration 301, with the exceptionsthat a tunable filter 1104 is operatively coupled between the dropmodule 302 and a tunable laser (transceiver) 1106, and an opticalamplifier 1102, such as an EDFA (erbium-doped fiber amplifier) opticalamplifier, is operatively coupled between the tunable laser(transceiver) 1106 and the add module 310, thereby providing the directconnection between fiber #1 (in) and fiber #1 (out) within the opticalMUX/DMUX module 202. It is noted that an EDFA optical amplifier, atunable filter, and a tunable laser (transceiver) may be operativelycoupled in an analogous fashion in the optical filter configuration 303(see FIG. 3 c) to provide a direct connection between fiber #7 (in) andfiber #7 (out) within the optical MUX/DMUX module 202.

It was also described above that the plurality of optical connectionpaths of the optical filter configuration 301 (see FIGS. 3 a, 3 b), suchas the optical connection paths 388-391, as well as the plurality ofoptical connection paths of the optical filter configuration 303 (seeFIGS. 3 a, 3 c), such as the optical connection paths 392-395, can beconfigured to provide one or more WDM (CWDM, or DWDM) wavelengthchannels between optical nodes 1-11 on the optical ring network 100 (seeFIG. 1). To implement the respective optical connection paths of theoptical filter configurations without requiring the use of WDM optics,exemplary optical configurations 1201, 1203 (see FIGS. 12 a, 12 b) maybe employed in place of the optical filter configurations 301, 303,respectively, within the optical MUX/DMUX module 202 (see FIG. 2, 3 a).It is noted, however, that, whereas the optical filter configurations301, 303 require the use of multi-fiber ribbon cables having at leasttwelve (12) fibers (e.g., fiber #1 through fiber #12; see FIGS. 3 b, 3c), the optical configurations 1201, 1203 require the use of multi-fiberribbon cables having at least forty-four (44) fibers (e.g., fiber #1through fiber #44; see FIGS. 12 a, 12 b). Further, whereas the opticalfilter configurations 301, 303 can support up to at least four (4) WDMwavelength channels between optical nodes 1-11 on the optical ringnetwork 100, the optical configurations 1201, 1203 can support a singlechannel between such optical nodes.

With regard to the optical configuration 1201 (see FIG. 12 a), fiber #1(in) can be used in conjunction with fiber #1 (out) to implement aconnection through at least the circuit switch 348 (see FIG. 3 a) for anOSC channel. Further, fiber #2 (in) can be used in conjunction withfiber #2 (out) to implement a point-to-point connection through at leastthe circuit switch 348 (see FIG. 3 a). Single and multi-hop connectionpaths can also be implemented using the optical configuration 1201 (seeFIG. 12 a) for optical signal transmission in the “West In”/“East Out”direction, as follows:

(1) fiber #3 (in) can be used in conjunction with fiber #4 (out) toimplement a one (1) hop connection through at least the circuit switch348 (see FIG. 3 a);

(2) fiber #5 (in) can be used in conjunction with fiber #7 (out) toimplement a two (2) hop connection through at least the circuit switch348 (see FIG. 3 a);

(3) fiber #8 (in) can be used in conjunction with fiber #11 (out) toimplement a two (3) hop connection through at least the circuit switch348 (see FIG. 3 a);

(4) fiber #12 (in) can be used in conjunction with fiber #16 (out) toimplement a two (4) hop connection through at least the circuit switch348 (see FIG. 3 a); and

(5) fiber #17 (in) can be used in conjunction with fiber #22 (out) toimplement a two (5) hop connection through at least the circuit switch348 (see FIG. 3 a).

With regard to the optical configuration 1203 (see FIG. 12 b), fiber #23(in) can be used in conjunction with fiber #23 (out) to implement aconnection through at least the circuit switch 348 (see FIG. 3 a) for anOSC channel. Further, fiber #24 (in) can be used in conjunction withfiber #24 (out) to implement a point-to-point connection through atleast the circuit switch 348 (see FIG. 3 a). Single and multi-hopconnections can also be implemented using the optical configuration 1203(see FIG. 12 b) for optical signal transmission in the “East In”/“WestOut” direction, as follows:

(1) fiber #25 (in) can be used in conjunction with fiber #26 (out) toimplement a one (1) hop connection through at least the circuit switch348 (see FIG. 3 a);

(2) fiber #27 (in) can be used in conjunction with fiber #29 (out) toimplement a two (2) hop connection through at least the circuit switch348 (see FIG. 3 a);

(3) fiber #30 (in) can be used in conjunction with fiber #33 (out) toimplement a two (3) hop connection through at least the circuit switch348 (see FIG. 3 a);

(4) fiber #34 (in) can be used in conjunction with fiber #38 (out) toimplement a two (4) hop connection through at least the circuit switch348 (see FIG. 3 a); and

(5) fiber #39 (in) can be used in conjunction with fiber #44 (out) toimplement a two (5) hop connection through at least the circuit switch348 (see FIG. 3 a).

It was further described above that the links interconnecting opticalnodes 1-11 on the optical ring network 100 (see FIG. 1) can beimplemented using a single optical fiber pair configuration, ormulti-fiber pair configurations including, e.g., one or more multi-fiberribbon cables. Such links interconnecting optical nodes 1-11 on theoptical ring network 100 can also be implemented using multi-coreoptical fiber.

FIG. 13 a depicts an exemplary multi-core optical fiber 1300 that may beemployed in conjunction with the optical MUX/DMUX module 202 (see FIGS.2, 3 a). As shown in FIG. 13 a, the multi-core optical fiber 1300includes a plurality of cores 1 through 6, in which each core 1-6 isoperative to carry an independent optical signal. FIG. 13 b depicts howsuch multi-core optical fiber may be employed in conjunction with theoptical filter configuration 301 (see FIGS. 3 a, 3 b) included in theoptical MUX/DMUX module 202. With regard to the optical filterconfiguration 301, a multi-core optical fiber 1300 a can be providedthat has a plurality of cores 1-6, which can correspond to fibers #1-#6,respectively, in the “West In” direction along the optical ring network100 (see FIG. 1). With further regard to the optical filterconfiguration 301, a multi-core optical fiber 1300 b can be providedthat has a plurality of cores 1-6, which can correspond to fibers #1-#6,respectively, in the “East Out” direction along the optical ring network100 (see FIG. 1). It is noted that, with regard to the optical filterconfiguration 303 (see FIGS. 3 a, 3 c), multi-core optical fibers can beprovided with pluralities of cores corresponding to the respectivefibers #7-#12 in the “East In” direction along the optical ring network100 (see FIG. 1), and the respective fibers #7-#12 out the “West Out”direction along the optical ring network 100 (see FIG. 1).

It was also described above with reference to the switch module 209 (seeFIGS. 2, 3 a) that the circuit switch 348 and the packet switch 346 canbe implemented as separate switches. Such switches can also beimplemented as a combined (“hybrid”) switch 1400 a, as depicted in FIG.14 a. For example, the hybrid switch 1400 a can be implemented as asingle integrated circuit (IC), using a field programmable gate array(FPGA), or any other suitable IC implementation technology. As shown inFIG. 14 a, the hybrid switch 1400 a includes a circuit switch 1402 and apacket switch 1404. The circuit switch 1402 can be connected torespective optical connection paths within the optical MUX/DMUX module202 via a plurality of input/output transceivers 1406. Further, thepacket switch 1404 can be connected to one or more servers via aplurality of downlink/downlink port connections 1408. Moreover, thecircuit switch 1402 can be connected to the packet switch 1404 by aplurality of port connections, such as 10 Gb/s port connections, withinthe hybrid switch 1400, or a custom ASIC incorporating the circuit andpacket switch functions.

FIG. 14 b depicts an exemplary alternative embodiment 1400 b of thehybrid switch 1400 a of FIG. 14 a. As shown in FIG. 14 b, thealternative embodiment 1400 b includes a circuit switch 1403 and apacket switch 1405. The circuit switch 1403 can be connected torespective optical connection paths within the optical MUX/DMUX module202 via a plurality of input/output transceivers 1407. Further, thepacket switch 1405 can be connected to one or more servers via aplurality of downlink/downlink port connections 1409. Moreover, thecircuit switch 1403 can be connected to the packet switch 1405 by aplurality of port connections, such as 10 Gb/s port connections. Inaddition, the circuit switch 1403 can be connected to one or moreservers via a plurality of programmable links 1411, thereby bypassingthe packet switch 1405 and providing a direct attach.

It is noted that the circuit switch 348 (see FIG. 3 a) can beimplemented using multiple circuit switches. FIG. 14 c depicts a hybridswitch 1400 c that includes a circuit switch 1418 and a packet switch1420. Like the hybrid switch 1400 a (see FIG. 14 a), the hybrid switch1400 c can be implemented as a single integrated circuit (IC), using afield programmable gate array (FPGA), or any other suitable ICimplementation technology. The circuit switch 1400 c includes aplurality of circuit switches 1418.1, 1418.2, 1418.3, 1418.4 operativelyconnected between a plurality of input/output transceivers 1416 and thepacket switch 1420. For example, if the packet switch 1420 is configuredto provide up to forty-eight (48) uplink ports, then each of theplurality of circuit switches 1418.1, 1418.2, 1418.3, 1418.4 can beimplemented as a 48×48 circuit switch. It is noted that, if a singlecircuit switch were employed in the hybrid switch 1400 c in place of theplurality of circuit switches 1418.1-1418.4, then the single circuitswitch may be implemented as a single 96×96 circuit switch.

In addition, it was described above that a selected pair of opticalnodes on an optical ring network can be configured to support a flywaychannel. FIG. 15 depicts an alternative embodiment 1500 of optical node1 of FIG. 3 a, in which optical node 1 is configured to support one ormore flyway channels on an optical ring network. Dedicated flyways existwhen the number of ports connected to the optical input/outputtransceivers, such as the input transceivers 1550.1-1550.14,1556.1-1556.14 and the output transceivers 1552.1-1552.14,1554.1-1554.14, exceed the number or ports connected to the packetswitch, such as the packet switch 1546, excluding any WDM/SDM channelsthat have been dedicated as control channels, as shown in FIG. 15. It isnoted that one or more of optical nodes 2-11 can be similarly configuredto support flyway channels, in accordance with the alternativeembodiment 1500 of FIG. 15. As shown in FIG. 15, the alternativeembodiment 1500 includes an optical MUX/DMUX module 1502 and a switchmodule 1509. The optical MUX/DMUX module 1502 includes a pair of opticalfilter configurations 1501, 1503 that can be used to implement a hybridSDM/WDM shifting channel plan. The optical filter configuration 1501includes a plurality of inputs (generally indicated by reference numeral1580) operatively connected to optical fibers #1 through #6 in the West(counter clockwise) direction along an optical ring network, such as theoptical ring network 100 (see FIG. 1), and a plurality of outputs(generally indicated by reference numeral 1582) operatively connected tooptical fibers #1 through #6 in the East (clockwise) direction along theoptical ring network 100. Likewise, the optical filter configuration1503 includes a plurality of inputs (generally indicated by referencenumeral 1584) operatively connected to optical fibers #7 through #12 inthe East (clockwise) direction along the optical ring network 100, and aplurality of outputs (generally indicated by reference numeral 1586)operatively connected to optical fibers #7 through #12 in the West(counter clockwise) direction along the optical ring network 100. Forexample, optical fibers #1 through #12 can be implemented using one ormore multi-fiber ribbon cables. It is noted that such multi-fiber ribboncables are described herein as including twelve (12) optical fibers forpurposes of illustration, and that any other suitable number of opticalfibers within such multi-fiber ribbon cables may be employed.

With reference to the alternative embodiment 1500 of FIG. 15, theplurality of inputs 1580 of the optical filter configuration 1501 areoperative to receive optical signals carried by the respective opticalfibers #1-#6 from, e.g., optical node 11 (see FIG. 1), and the pluralityof outputs 1582 of the optical filter configuration 1501 are operativeto send optical signals on the respective optical fibers #1-#6 to, e.g.,optical node 2 (see FIG. 1). In the East (clockwise) direction along theoptical ring network 100 (see FIG. 1), the alternative embodiment 1500of optical node 1 is therefore communicably coupled to optical node 11by the plurality of inputs 1580, which are in a predetermined sequencecorresponding to the fibers #1 through #6. Further, the alternativeembodiment 1500 of optical node 1 is communicably coupled, in the East(clockwise) direction along the optical ring network 100, to opticalnode 2 by the plurality of outputs 1582, which are also in thepredetermined sequence corresponding to the fibers #1 through #6.

The plurality of inputs 1584 of the optical filter configuration 1503(see FIG. 15) are operative to receive optical signals carried by therespective optical fibers #7 through #12 from, e.g., optical node 2 (seeFIG. 1), and the plurality of outputs 1586 of the optical filterconfiguration 1503 (see FIG. 15) are operative to send optical signalson the respective optical fibers #7 through #12 to, e.g., optical node11 (see FIG. 1). In the West (counter clockwise) direction along theoptical ring network 100, the alternative embodiment 1500 of opticalnode 1 is therefore communicably coupled to, e.g., optical node 2 (seeFIG. 1), by the plurality of inputs 1584, which are in a predeterminedsequence corresponding to the fibers #7 through #12. Further, thealternative embodiment 1500 of optical node 1 is coupled, in the West(counter clockwise) direction along the optical ring network 100, to,e.g., optical node 11 (see FIG. 1), by the plurality of outputs 1586,which are also in the predetermined sequence corresponding to the fibers#7 through #12.

As shown in FIG. 15, the switch module 1509 includes a packet switch1546, and a circuit switch 1548 disposed between the packet switch 1546and the respective optical filter configurations 1501, 1503. The circuitswitch 1548 can receive, in electrical form, one or more signals sourcedfrom one or more of the inputs 1580, 1584, and can provide one or moreof the signals for subsequent forwarding as optical signals to one ormore of the outputs 1582, 1586. It is noted that the switch module 1509can further include a processor for local control and/or configurationof the packet switch 1546 and/or the circuit switch 1548. Such aprocessor can receive instructions for such control and/or configurationof the packet switch 1546 and/or the circuit switch 1548 from anexternal central processor over an optical supervisory control (OSC)channel corresponding to a drop module 1512 and an add module 1520within the optical filter configuration 1501, and/or an OSC channelcorresponding to a drop module 1537 and an add module 1530 within theoptical filter configuration 1503. Such a processor can also beconfigured to receive instructions via a network management port. Theprocessor for local control and/or configuration of the packet switch1546 and/or the circuit switch 1548 has been omitted from FIG. 15 forclarity of illustration. The switch module 1509 also includes aplurality of input transceivers 1550.1-1550.14 and a plurality of outputtransceivers 1552.1-1552.14 disposed between the circuit switch 1548 andthe optical filter configuration 1501, as well as a plurality of inputtransceivers 1556.1-1556.14 and a plurality of output transceivers1554.1-1554.14 disposed between the circuit switch 1548 and the opticalfilter configuration 1503. It is further noted that clock and datarecovery (CDR) may be implemented, as required and/or as desired, eitheras an integrated part of the circuit switch 1548, or externally. CDRcircuits have been omitted from FIG. 15 for clarity of illustration.

As further shown in FIG. 15, the optical filter configuration 1501includes a plurality of drop modules 1514, 1516, and a plurality of addmodules 1518, 1522, 1524, 1526, 1528. Each of the drop modules 1514,1516 is operative to separate one or more optical signals, such as WDMwavelength channel signals allocated to one or more predetermined WDMwavelength channels, from one or more optical signals received overfiber #1 (in) and/or fiber #2 (in). In addition, each of the add modules1518, 1522, 1524, 1526, 1528 is operative to add one or more opticalsignals, such as WDM wavelength channel signals allocated to one or morepredetermined WDM wavelength channels, to one or more optical signalsfor transmission over fiber #1 (out), fiber #3 (out), fiber #4 (out),fiber #5 (out), and/or fiber #6 (out). Like the optical filterconfiguration 1501, the optical filter configuration 1503 includes aplurality of drop modules 1534, 1536, and a plurality of add modules1532, 1538, 1540, 1542, 1544. Each of the drop modules 1534, 1536 isoperative to separate one or more optical signals, such as WDMwavelength channel signals allocated to one or more predetermined WDMwavelength channels, from one or more optical signals received overfiber #7 (in) and/or fiber #8 (in). In addition, each of the add modules1532, 1538, 1540, 1542, 1544 is operative to add one or more opticalsignals, such as WDM wavelength channel signals allocated to one or morepredetermined WDM wavelength channels, to one or more optical signalsfor transmission over fiber #7 (out), fiber #9 (out), fiber #10 (out),fiber #11 (out), and/or fiber #12 (out).

The plurality of input transceivers 1550.1-1550.14 are operative toperform optical-to-electrical (O-E) conversion of wavelength channelsignals separated from the optical signals received over fiber #1 (in)and/or fiber #2 (in), and the plurality of output transceivers1552.1-1552.14 are operative to perform electrical-to-optical (E-O)conversion of the wavelength channel signals to be added to the opticalsignals for transmission over fiber #1 (out), fiber #3 (out), fiber #4(out), fiber #5 (out), and/or fiber #6 (out). Likewise, the plurality ofinput transceivers 1556.1-1556.14 are operative to performoptical-to-electrical (O-E) conversion of the wavelength channel signalsseparated from the optical signals received over fiber #7 (in) and/orfiber #8 (in), and the plurality of output transceivers 1554.1-1554.14are operative to perform electrical-to-optical (E-O) conversion of thewavelength channel signals to be added to the optical signals fortransmission over fiber #7 (out), fiber #9 (out), fiber #10 (out), fiber#11 (out), and/or fiber #12 (out).

The circuit switch 1548 is operative to receive, in electrical form fromone or more of the input transceivers 1550.1-1550.14, 1556.1-1556.14,one or more wavelength channel signals via the optical filterconfiguration 1501 and/or the optical filter configuration 1503. Thecircuit switch 1548 is further operative to selectively provide one ormore of the wavelength channel signals to the packet switch 1546, and/orto selectively provide one or more of the wavelength channel signals toone or more of the output transceivers 1552.1-1552.14, 1554.1-1554.14.Such wavelength channel signals can, in turn, be provided by the outputtransceivers 1552.1-1552.14, 1554.1-1554.14, in optical form, to one ormore of the add modules 1518, 1522, 1524, 1526, 1528, 1532, 1538, 1540,1542, 1544, for subsequent addition to one or more optical signals fortransmission over fiber #1(out), one or more of fibers #3-6 (out), fiber#7 (out), and/or one or more of fibers #9-12 (out).

As described above, the alternative embodiment 1500 (see FIG. 15) ofoptical node 1 (see also FIG. 3 a) is configured to support one or moreflyway channels on an optical ring network. To that end, a predeterminednumber of input/output transceivers, such as the twenty-eight (e.g.,p=28) input transceivers 1550.1-1550.14 and output transceivers1552.1-1552.14, are communicably coupled between the optical filterconfiguration 1501 and the circuit switch 1548. Likewise, apredetermined number of input/output transceivers, such as thetwenty-eight (p=28) input transceivers 1556.1-1556.14 and outputtransceivers 1554.1-1554.14, are communicably coupled between theoptical filter configuration 1503 and the circuit switch 1548. It isnoted that any other suitable number of input/output transceivers may besimilarly coupled between the respective optical filter configurations1501, 1503 and the circuit switch 1548. Further, the circuit switch 1548can be configured to communicably couple, over a connection 1590, apredetermined number, such as twenty-four (e.g., q=24) or any othersuitable number, of the twenty-eight (p=28) input/output transceivers1550.1-1550.14, 1552.1-1552.14 or 1556.1-1556.14, 1554.1-1554.14 to thepacket switch 1546. The remaining four (i.e., (p−q)=(28−24)=4)input/output transceivers among the input/output transceivers1550.1-1550.14, 1554.1-1554.14, as well as the remaining four (i.e.,(p−q)=(28−24)=4) input/output transceivers among the input/outputtransceivers 1556.1-1556.14, 1552.1-1552.14, may be employed toimplement the flyway channels on the optical ring network.

For example, the circuit switch 1548 may be configured to communicablycouple the twelve (12) input transceivers 1550.1-1550.12 and the twelve(12) output transceivers 1554.1-1554.12 to the packet switch 1546,thereby providing wavelength channel signals allocated to wavelengthchannels 1, 2, 3, 4, from the drop module 1514, as well as wavelengthchannel signals allocated to wavelength channels 1, 2, 3, 4, 5, 6, 7, 8from the drop module 1516, to the packet switch 1546 over the connection1590. The remaining four (4) input/output transceivers, namely, theinput transceivers 1550.13, 1550.14 and the output transceivers 1552.13,1552.14, may be employed to implement two (2) flyway channels. One suchflyway channel can carry a wavelength channel signal allocated towavelength channel 9 from fiber #2 (in), through the drop module 1516,the input transceiver 1550.13, the circuit switch 1548, the outputtransceiver 1552.13, and the add module 1528, to fiber #6 (out). Anothersuch flyway channel can carry a wavelength channel signal allocated towavelength channel 10 from fiber #2 (in), through the drop module 1516,the input transceiver 1550.14, the circuit switch 1548, the outputtransceiver 1552.14, and the add module 1528, to fiber #6 (out).Dedicated flyway wavelengths can be added to any other input/outputpairs, provided the flyway wavelength added is dropped in a mannerconsistent with the WDM/SDM channel plan. In fact, any unused lightpathsbetween optical nodes can be used to form dedicated flyway wavelengths.

Similarly, the circuit switch 1548 may be configured to communicablycouple the twelve (12) input transceivers 1556.1-1556.12 and the twelve(12) output transceivers 1552.1-1552.12 to the packet switch 1546,thereby providing wavelength channel signals allocated to wavelengthchannels 1, 2, 3, 4 from the drop module 1534, as well as wavelengthchannel signals allocated to wavelength channels 1, 2, 3, 4, 5, 6, 7, 8from the drop module 1536, to the packet switch 1546 over the connection1590. The remaining four (4) input/output transceivers, namely, theinput transceivers 1556.13, 1556.14 and the output transceivers 1554.13,1554.14, may be employed to implement two (2) additional dedicatedflyway channels. One such dedicated flyway channel can carry awavelength channel signal allocated to wavelength channel 9 from fiber#8 (in), through the drop module 1536, the input transceiver 1556.13,the circuit switch 1548, the output transceiver 1554.13, and the addmodule 1544, to fiber #12 (out). Another such dedicated flyway channelcan carry a wavelength channel signal allocated to wavelength channel 10from fiber #8 (in), through the drop module 1536, the input transceiver1556.14, the circuit switch 1548, the output transceiver 1554.14, andthe add module 1544, to fiber #12 (out). It is noted that any otherinput/output transceivers may be selected from among the input/outputtransceivers 1550.1-1550.14, 1552.1-1552.14, and from among theinput/output transceivers 1556.1-1556.14, 1554.1-1554.14, to implementany other suitable number of dedicated flyway channels on an opticalring network.

It is noted that the operations depicted and/or described herein arepurely exemplary. Further, the operations can be used in any sequence,when appropriate, and/or can be partially used. With the aboveillustrative embodiments in mind, it should be understood that suchillustrative embodiments can employ various computer-implementedoperations involving data transferred or stored in computer systems.Such operations are those requiring physical manipulation of physicalquantities. Typically, though not necessarily, such quantities take theform of electrical, magnetic, and/or optical signals capable of beingstored, transferred, combined, compared, and/or otherwise manipulated.

Further, any of the operations depicted and/or described herein thatform part of the illustrative embodiments are useful machine operations.The illustrative embodiments also relate to a device or an apparatus forperforming such operations. The apparatus can be specially constructedfor the required purpose, or can be a general-purpose computerselectively activated or configured by a computer program stored in thecomputer to perform the function of a particular machine. In particular,various general-purpose machines employing one or more processorscoupled to one or more computer readable media can be used with computerprograms written in accordance with the teachings disclosed herein, orit may be more convenient to construct a more specialized apparatus toperform the required operations.

Instructions for implementing the systems and methods disclosed hereincan also be embodied as computer readable code on a computer readablemedium. The computer readable medium is any data storage device that canstore data, which can thereafter be read by a computer system. Examplesof such computer readable media include magnetic and solid state harddrives, read-only memory (ROM), random-access memory (RAM), Blu-Ray™disks, DVDs, CD-ROMs, CD-Rs, CD-RWs, magnetic tapes, and/or any othersuitable optical or non-optical data storage device. The computerreadable code can be stored in a single location, or stored in adistributed manner in a networked environment.

The foregoing description has been directed to particular illustrativeembodiments of this disclosure. It will be apparent, however, that othervariations and modifications may be made to the described embodiments,with the attainment of some or all of their associated advantages.Moreover, the procedures, processes, and/or modules described herein maybe implemented in hardware, software, embodied as a computer-readablemedium having program instructions, firmware, or a combination thereof.For example, the functions described herein may be performed by aprocessor executing program instructions out of a memory or otherstorage device.

It will be appreciated by those skilled in the art that modifications toand variations of the above-described systems and methods may be madewithout departing from the inventive concepts disclosed herein.Accordingly, the disclosure should not be viewed as limited except as bythe scope and spirit of the appended claims.

What is claimed is:
 1. A method of multicasting an Ethernet frame froman origin Ethernet switch to at least one destination port on adestination Ethernet switch over at least one path, comprising the stepsof: specifying at least one duplex port of the origin Ethernet switch asa multicast master port; specifying a destination Ethernet switch as aprimary destination switch for each multicast master port; specifyingone duplex port of the primary destination switch as a primarydestination port for each of the multicast master ports; establishing aforward simplex connection from each of the at least one duplex ports ofthe origin Ethernet switch to its primary destination port through oneor more circuit switches in the at least one path between and includingthe origin Ethernet switch and the primary destination switch;populating a forwarding table associated with the origin Ethernet switchwith MAC addresses of frames to be multicast towards the destinationswitches, the destination switches including the primary destinationswitch; populating a forwarding table of each destination switch with anoutput port mapping based on, but not limited to, packet header fieldsfor a received Ethernet frame; forwarding the Ethernet frame from theorigin Ethernet switch on the forward simplex connection for receipt bythe primary destination switch; creating at least a first and secondcopy of the Ethernet frame at the output of one or more circuitswitches; and directing the first copy of the Ethernet frame from thecircuit switch to the multicast master port.
 2. A method of multicastingan Ethernet frame from an origin Ethernet switch to at least twodestination ports on at least two destination Ethernet switches over atleast two paths, comprising the steps of: specifying at least one duplexport of the origin Ethernet switch as a multicast master port;specifying a first destination Ethernet switch as a primary destinationswitch for each multicast mater port; specifying one duplex port of theprimary destination switch as a primary destination port for each of themulticast master ports; specifying a second destination Ethernet switchas a secondary destination switch; specifying one duplex port of thesecondary destination switch as a secondary destination port for each ofthe multicast master ports; establishing a duplex connection betweeneach multicast master port and its primary destination port through oneor more cross-point switches, the duplex connection including a forwardsimplex connection from the multicast master port and a reverse simplexconnection from the primary destination port to the multicast masterport; populating a forwarding table associated with the origin Ethernetswitch with MAC addresses of frames to be multicast towards thedestination switches, the destination switches including the primarydestination switch; populating a forwarding table of each destinationswitch with MAC addresses of frames to be multicast towards thedestination switches to be forwarded to one or more ports of thedestination switch; creating at least first and second copies of theforward simplex connection at one or more outputs of the one or morecross-point switches; and directing at least one of the first and secondcopies of the forward simplex connection to the secondary destinationport of the secondary destination switch.
 3. The method of claim 2wherein the primary destination switch is the same as the origin switchand the primary destination port is the same as the multicast masterport.